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Me  ctiani  c  s   De ID t . 

The  Penton  Publishing  Co. 

Cleveland,  O.,  U.  S.  A. 
Publishers  of 

The  Foundry      The  Iron  Trade  Review 
Marine  Review  Daily  Metal  Trade 

Power  Boating  Abrasive  Industry 




By  H.  A.  Schwartz 

First  Edition 

Published  by 

The  Penton  Publishing  Co. 

Cleveland,  Ohio 



Copyright  in  the  United  States 

Entered  at  Stationers'  Hall,  London 


The  Penton  Publishing  Co. 
Cleveland,  Ohio 







THE  literature  of  malleable  cast  iron,  in  the  American  sense 
of  that  term,  is  limited  to  a  single  book  first  issued  about 
10  years  ago  and  now  out  of  print,  and  to  a  series  of  articles 
of  great  diversity  of  character  and  quality  in  the  technical  publi- 
cations of  this  country  and  Europe.     Much  of  the  most  valuable 
scientific  matter  is  buried  in  the  purely  scientific  press,  frequently 
under   titles    which   do   not    suggest   its   application   to    any   one 
not  a  specialist  in  metallurgy. 

Under  these  circumstances  the  preparation  of  a  new  book 
dealing  with  American  malleable  cast  iron  in  theory  and 
practice  may  serve  a  useful  purpose  as  summarizing  and  rec- 
ording, so  far  as  any  book  can,  the  contemporary  state  of  the 
art  in  the  metallurgy  of  this  product. 

If  in  the  following  pages  the  specialist  finds  much  which  ap- 
pears to  him  elemental  or  trivial  or  the  non  technical  reader  finds 
matter  which  appears  too  complex,  the  author  must  plead  in  ex- 
tenuation his  desire  to  prepare  a  book  to  suit  many  kinds  of 

This  has  necessitated  the  inclusion  of  much  elementary 
matter  both  in  metallurgy  and  mechanics  which  will  be  useful 
only  in  acquainting  -the  lay  reader  with  the  interpretation  of 
terms  and  data  which  form  the  every  day  vocabulary  of  the 

On  the  other  hand  it  has  seemed  that  in  order  that  the 
reader  might  secure  full  value  from  a  reading  of  these 
pages  no  known  fact  or  theory  should  be  excluded  merely  in  the 
interest  of  simplicity. 

Feeling  that  no  single  individual  is  justified  in  the  belief  that 
his  own  views  are  final  in  so  complex  a  subject  the  author 
has  not  hesitated  to  refer  freely  to  the  literature  and  even  to 
record  opinions  contrary  to  his  own.  So  far  as  possible  due 
credit  has  been  given  in  all  such  cases. 

Guided  by  the  injunction  of  Leonardo  da  Vinci,  "Con- 
firm your  statements  by  examples  and  not  by  assertions",  it  has 


been  the  author's  constant  effort  to-  record  facts  rather  than 
opinions  wherever  possible.  This  has  been  particularly  true 
in  the  chapters  dealing  with  manufacturing  methods.  In  these 
chapters  the  record  is  one  of  what  has  been  rather  than  of  what 
might  be  accomplished.  Much  of  the  experimental  work  re- 
ferred to  is  the  work  of  the  author's  associates.  In  this  connec- 
tion special  recognition  must  be  given  to  the  very  unusual  micro- 
graphs which  are  the  work  of  Harrie  R.  Payne,  chief  chemist 
and  metallographer  of  the  author's  laboratory. 

Many  of  the  author's  friends  within  the  malleable  industry, 
in  the  organization  of  which  he  has  the  honor  to  be  a  member, 
and  among  the  business  connections  of  that  association  have 
contributed  valuable  information. 

Whenever  possible  credit  has  been  assigned.  In  some  cases 
where  for  obvious  reasons  it  was-  improper  to  identify  the  in- 
formation the  latter  has  consented  to  the  anonymous  presenta- 
tion of  his  material.  The  co-operation  of  the  American  Malle- 
able Castings  Association  in  furnishing  statistics  and  of  the 
late  Thos.  Devlin  of  Philadelphia,  and  Alfred  E.  Hammer, 
Branford,  Conn.,  in  contributing  historic  matter  from  their  long 
experience  is  especially  worthy  of  grateful  acknowledgment. 

If  the  following  pages  contain  any  information  calculated 
to  dispel  the  many  misconceptions  as  to  malleable  cast  iron  and 
to  acquaint  the  interested  reader  accurately  with  the  proper- 
ties and  methods  of  manufacture  of  this  interesting,  valuable  and 
characteristically  American  product,  the  author's  labor  will 
have  been  richly  repaid. 




Early    History    of    Ironmaking     1 


Development  of  Malleable  Industry  in  the  United  States    15 

Metallurgy   of    Malleable    Iron    41 


General    Manufacturing    and     Plant     71 


Melting     Stock     91 


Fuel    and    Refractories     109 


Air     Furnace     Melting     135 


Electric     Furnace     Melting     159 


Cupola    and    Open-hearth    Melting     175 


Annealing    Practice     189 


Principles    of    Annealing    213 


Molding    and    Patternmaking    .* 233 


Cleaning    and    Finishing    249 


Inspecting    and     Testing     " 267 


Tensile     Properties     287 

Compression,   Bending  and    Shear 303 

Fatigue,    Impact,    Hardness    and    Wear    315 

Plastic    Deformation    339 


Thermal  and  Electrical    Properties 371 

Selected     Bibliography     385 

Index     403 



Fig.   1 — A  meteorite  -  in  the  American  Museum  of   Natural   History, 

New  York,  brought  from  Greenland  by  Admiral   Peary    2 

Fig.  2 — A  primitive  furnace,  1500  B.  C.  The  illustration  was  re- 
produced from  an  Egyptian  wall  painting 

Fig.    3 — One    of    the    earliest    blast    furnaces    4 

Fig.    4 — An    early    American    blast    furnace     7 

Fig.    5 — Reaumur's    foundry  in    1724.      One    furnace   has    just    been 

emptied  and  the  blast  is  being  applied  to  the  other    

Fig.  6 — Statue  of  Seth  Boyden,  erected  in  the  city  park  of  Newark, 
N.  JM  by  citizens  in  memory  of  the  man  who  laid  the  founda- 
tion for  the  malleable  industry  in  the  United  States  12 

Fig.     7— Seth     Boyden 16 

Fig.    8 — J.    H.    Barlow,    Boyden's    successor     16 

Fig.  9 — Distribution  of  malleable  iron  foundries  in  the  United 
States.  The  dots  represent  the  location  of  malleable  foundries 

according  to  data  compiled  for  government  use    : . . . .         20 

Fig.  10 — Map  showing  location  of  principle  sellers  of  malleable  iron 

castings    in    the    United    States 22 

Fig.    11 — Comparison    of    production    of    steel    and    malleable    iron 

castings     24 

Fig.  12 — Familiar  figures  in  the  development  of  the  malleable  in- 
dustry in  the  United  States 28 

Fig.    13 — Three  metallurgists   who  have  been  closely  identified  with 

the   technical    advancement    of    the    industry 32 

Fig.   14 — The  names   of   these  men  are  linked  with  the  rise  of   the 

American     malleable     industry 34 

Fig.   15 — Austenite  and  ledeburite  in  manganiferous   white  cast  iron        42 

Fig.    16 — Martensite    in    quenched    white    cast    iron     42 

Fig.     17— Troostite    in    steel 43 

Fig.    18 — Pearlite    in    incompletely    annealed    malleable    43 

Fig.     19 — Spheroidized     pearlite 44 

Fig.    20 — Graphite    in    gray    iron 44 

Fig.    21 — Soft    gray    cast    iron     45 

Fig.    22 — Malleable    cast    iron 45 

Fig.  23 — Benedict's  diagram  recording  the  equilibrium  conditions  in 
terms  of  temperature  and  agraphic  (non  graphitic)  carbon. 

It  is  based  on  Benedict's  principle,  somewhat  modified    47 

Fig.    24— A    further    modification    of    Benedict's    diagram    indicating 

the  results  of  recent  research  work   51 

Fig.  25 — Graphite  crystals  in  malleable  made  from  hard  iron  con- 
taining graphite  54 

Fig.  26 — Unannealed  hard  iron.     The   structure  is   always   dendritic 

but    varies    slightly    with    the    carbon    content    55 




Fig.  27 — Effect  of  silicon  in  relation  to  carbon  on  malleable.  This 

graph  is  based  on  data  from  Thrasher's  determinations  56 

Fig.  28 — Beginning  of  graphitization  after  one  half  hour  at  1700 

degrees  Fahr 58 

Fig.  29 — Progress  of  graphitization  after  \l/2  hours  at  1700  degrees 

Fahr 58 

Fig.  30 — Progress  of  graphitization  after  3l/2  hours  at  1700  de- 
grees Fahr 60 

Fig.  31 — Equilibrium  at  1700  degrees  Fahr.  after  70  hours   60 

Fig.  32 — Imperfect  attainment  of  equilibrium  below  A±  due  to  too 

short  a  time 62 

Fig.  33 — Normal  malleable  iron,  metastable  equilibrium  below   At . .         62 

Fig.  34 — Graphite  crystals  produced  by  annealing  at  2100  degrees 

Fahr , 64 

Fig.  35 — Manganese  sulphide  in  a  malleable  cast  iron.  The  arrows 

point  to  MnS  64 

Fig.  36 — Chart  showing  conversion  of  combined  carbon  into  temper 

carbon  66 

Fig.  37 — Changes  of  metallographic  composition  during  the  freezing 

and  annealing  of  white  iron  69 

Fig.   38 — Organization    chart    for   malleable    foundry    72 

Fig.  39 — A  good  example  of  the  approved  style  of  architecture  for 

a  malleable  foundry  built  a  generation  ago  74 

Fig.  40 — Exterior  view  of  a  large  malleable  plant  built  about  1917        76 

Fig.  41 — Coreroom  of  a  modern  malleable  plant  showing  roof  con- 
struction designed  to  facilitate  removal  of  fumes  and  gases 
and  to  afford  good  natural  lighting  78 

Fig.  42 — Interior  of  the  annealing  department  of  a  modern 

malleable  foundry 80 

Fig.  43 — Chart  showing  cycle  of  principal  operations  in  a  malle- 
able plant  83 

Fig.  44 — Chart  showing  division  of  labor  in  a  typical  foundry   ....         84 

Fig.  45 — Molding  floor  in  a  well  organized  American  malleable 

foundry 86 

Fig.    45 — The    stock    yard    usually    is    served    by    a    traveling    crane        92 

Fig.  47— Map  showing  location  of  principal  ore  fields,  and  coke  and 

charcoal  blast  furnace  producing  malleable  pig  iron  95 

Fig.  48 — An  open  pit  iron  ore  mine  on  the  Mesabi  range.  Ores  in 

this  district  are  suitable  for  making  malleable  pig  98 

Fig.  49 — An  ore  loading  dock  at  one  of  the  ports  on  Lake 

Superior  100 



Fig.    50 — An   ore   unloading   dock   at    a  Lake   Erie   port,    where   the 

ore  is   transferred  from  ore  carrier  to  railroad  car    102 

Fig.  51 — A  charcoal  blast  furnace  in  Michigan  where  malleable  pig 

iron    is    made    104 

Fig.  52 — A  typical  coke  blast  furnace  in  the  Mahoning  valley    106 

Fig.  53 — Map  showing  location  of  principal  resources  of  metallurgi- 
cal   fuel   in   the   United    States .' 110 

Fig.   54 — A  modern   coal   tipple   in   West   Virginia    112 

Fig.  55 — Picking  table  in  a  coal  tipple  showing  facilities  for  remov- 
ing   slate,    sulphur,    etc.,    by    hand    114 

Fig.  56 — Adjustable  loading  boom  which  places  coal  in  car  without 

breakage     114 

Fig.    57 — A    modern    by-product    coke    plant    which    is    engaged    in 

making    foundry    fuel    116 

Fig.   58 — A  typical  scene  at  a  beehive  coke  oven  plant  in- the  Con- 

nellsville    region     118 

Fig.    59 — Cross    section    of    a   modern    gas    producer    120 

Fig.   60 — A   scene   in   an   important   oil    field   in   Oklahoma    122 

Fig.   61 — Operations   in   a  molding   sand  pit 125 

Fig.    62 — Hauling    sand    from    a    pit     125 

Fig.  63 — Map  showing  the   principal   sources  of   molding  sand,   fire- 
clay and  brick   in    the    United    States    126 

Fig.    64 — Open    fireclay   pit    covering    over    10    acres    and    with    bed 

of    clay    from   25   to   40    feet   thick    '. 128 

Fig.    65 — A    plant    in    Missouri    showing    round,    down-draft    kilns, 

factory  and  stock  sheds    130 

Fig.    66 — A    repress    room    in    a    Missouri    firebrick    plant,    showing 

machines    in   which    stiff   mud   firebrick   are   made    132 

Fig.   67 — Firebrick  and   special   fireclay   shapes    in   kiln   ready  to   be 

burned     133 

Fig.    68 — Sectional    drawings    showing    construction    of    typical    air 

furnace      136 

Fig.  69 — Graph  showing  recombination  of  carbon  in  pig  iron,...  139 
Fig.  70 — The  roof  of  the  modern  air  furnace  is  almost  straight..  140 
Fig.  71 — A  waste  heat  boiler  connected  to  two  air  furnaces.  Note 

that   coal    for   auxiliary   firing    is   on   hand    142 

Fig.    72 — Gray   sprue    148 

Fig.   73 — Gray   sprue   showing  white   patches.    Characteristic   of   less 

but   still    excessive   carbon   and    silicon    148 

Fig.   74 — Moderately  mottled   sprue  characteristic   of   carbon,   silicon 

and  temperature  suited  to  very  small  work    148 



Fig.   75 — Normal   sprue   for   metal   of   the   higher   carbon   ranges   of 

specification    metal    in     average    work 149 

Fig.   76 — Similar  to  Fig.   74  but  lower  in  carbon    149 

Fig.  77 — Similar  to  Fig.  76  but  quite  low  carbon   149 

Fig.  78 — ''High"  iron  i.e.  metal  low  in  carbon,  silicon  and  man- 
ganese. Fracture  granular  throughout  and  edge  showing  blow- 
holes    149 

Fig.    79 — Changes    of    metal    after    tapping    151 

Fig.  80 — A  powdered  coal  atatchment  for  an  air  furnace  155 

Fig.   81 — Cupola   producing   molten    iron — the    starting    point    of    the 

Kranz    triplex    process 160 

Fig.    82 — Two-ton    side-blow   converter   producing   liquid    steel    from 

cupola   metal   in   triplex   process    162 

Fig.  83. — Transfer  train  consisting  of  electric  motor  car  and 
trailer  with'  crane  ladle.  This  equipment  is  used  in  carrying 

cupola  and  converter  metal  to  the  electric   furnaces    165 

Fig.    84 — Heroult    electric    furnace    in    which    cupola    and    converter 

metal  is  charged  for  final  step  in  triplex  process   168 

Fig.   85 — Heroult   furnace  tilted   for  pouring    170 

Fig.  86 — Pouring  side  of  open-hearth  furnace  for  malleable  iron..  176 
Fig.  87 — Charging  side  of  open-hearth  furnace  in  malleable  plant  . .  178 
Fig.  88 — Design  of  a  modern,  stationary  open-hearth  steel  furnace.  180-181 
Fig.  89 — Separator  plate  designed  to  eliminate  use  of  packing 

with    annealing    pots     190 

Fig.  90 — A  view  of  the  annealing  department  in  a  modern  malleable 

castings    plant 194 

Fig.    91 — Charging    trucks    facilitate    the    handling    of    pots    to    and 

from    the    annealing    furnaces     195 

Fig.  92 — The  interior  of  the  powdered  coal  mill  of  a  modern  malle- 
able plant 197 

Fig.  93 — While  most  of  the  plants  in  the  United  States  employ 
annealing  furnaces  similar  to  those  shown  in  Fig.  90,  a  few 

plants  use  the  pit  type,  illustrated  above    198 

Fig.  94 — Diagram  showing  the  distribution  of  heat  in  a  continuous- 
type  annealing  furnace  200 

Fig.     95 — Interior    of     continuous-type    annealing     furnace     looking 

toward    the    entrance    end 200 

Fig.   96 — Single   section   of   combustion   chamber   of    continuous   type 

annealing    furnace 201 

Fig.  97 — A  sectional  plan  and  elevation  of  a  double-chamber,  car- 
type  tunnel  kiln  for  annealing  malleable  iron  castings.  The  fir- 



ing  zones  are  diagonally  opposite  each  other    202 

Fig.    98 — Rim   of    a   casting   containing   most    of    the   usual    defects 
due  to  annealing.     Etched  with  picric  acid,  magnified  100  diam-  ' 
eters   and   subsequently   reduced   one-fourth   on   erfgraving    ....216,217 

Fig.  99 — Increase  in  carbon  content  at  increasing  depths   below'  the 

surface    of    malleable    cast    iron    .........'... 223 

Fig.  100— Graph  showing  effect  of  removing  one-sixteenth  inch, 
decarborized  surface  in  specimens  of  various  diameters  on  the 
tensile  properties  of  the  metal  225 

Fig.    101 — Graph   showing   effect    of    varying    degrees    of    decarburi- 

zation  on  tensile  properties  of  malleable  cast  iron    226 

Fig.  102 — Equilibrium  curves  illustrating  the  reactions  between  car- 
bon, iron  and  oxygen,  after  the  data  of  Matsubara 230 

Fig.   103 — Methods  of  mounting  patterns 234 

Fig.    104 — Squeezer-type    molding    machine    and    mold    and    pattern 

equipment    in    place 236 

Fig.    105 — Stripper  and  rollover -type  molding  machines    238 

Fig.    106 — Curve   showing   contraction  in  cooling   from    solidification 

to    room    temperature 238 

Fig.   107 — Graph   showing  the  per   cent  of   contraction  of   malleable 

from  pattern  size    240 

Fig.    108 — Graphs    showing   relation   of    annealing   upon    the   density 

of    the   metal 241 

Fig.    109 — Casting  with  thin   disk  and   thick  hub,   showing  probable 

point    of    rupture     242 

Fig.    1-10 — Type   of    casting  with   thin   disk   center   and   thick   rim..       242 

Fig.  Ill — Dendrite  (about  half  size)  from  shrink  in  hard  iron 
ingot  8  inches  in .  diameter  by  20  inches  high  which  was 
poured  without  feeding 244 

Fig.  112 — Typical  gate  for  malleable  castings  showing  strainer,  core 
and  skimmer  gates  for  furnishing  clean  metal  for  feeders  and 
producing  sound  castings  246 

Fig.    113 — Tumbling   barrels   are  used   for   cleaning   castings    250 

Fig.    114 — Sand   blast   equipment    is   used    for    removing   sand    from 

castings 252 

Fig.  115 — Sorting  and  inspecting  small  castings  are  important  opera- 
tions in  many  plants  252 

Fig.  116 — When  machine  center  and  casting  center  are  not  concen- 
tric apparent  hard  spots  may  be  found  .-...- 255 

Fig.   117— (left) — Cementite  persisting  near  a  shrink.     The  metal  in 

porous  areas  is  somewhat  oxidized    257 




Fig.    118 — (Right) — Hard    slag    inclusions    just    below    the    surface 

which  may  dull  cutting  tools  rapidly 257 

Fig.  119 — Malleable  casting  effectively  arc  welded  with  Swedish  iron. 
The  changes  visible  microscopically  were  insufficient  to  make 
notable  difference  in  metal.  Area  A  is  soft  iron  but  very  slightly 
recarburized  from  the  malleable;  B  is  an  oxide  or  slag  film, 
and  C  is  the  malleable  showing  but  little  resolution  of  carbon 

due  to  close  confinement    258,  259 

Fig.  120 — Hard  iron  casting  successfully  acetylene  welded  with  hard 
iron  and  then  annealed.  Note  metallurgical  homogeneity  of 
casting  except  for  presence  of  slag.  A  is  the  original  casting, 
B  the  slag,  C  the  material  of  weld  as  noted  by  larger  grain 
size,  and  D  the  material  of  weld  as  noted  by  persistence  of  a 

little  pearlite  due  to  decarburization    258,  259 

Fig.  121 — Ineffective  hard  weld  of  malleable  casting  using  ingot 
iron  wire  and  acetylene  method.  Neither  material  has  its 
original  structure.  A  is  the  soft  iron  filler  converted  into  hard 
iron  by  migration  of  carbon  from  the  malleable.  B  is  the 
original  malleable  iron,  the  background  of  which  has  become 
sorbitic  due  to  recombination  of  carbon  at  temperature  the 

metal    reached   in   welding 258,  259 

Fig.   122 — Photomicrograph  showing  heavy  pearlitic  rim  which  may 

cause    machining    difficulties     262 

Fig.  123 — (Left) — An  effective  acetylene  weld,  malleable  becoming 
sorbitic  due  to  resolution  of  carbon.  A  is  gray  iron  converted 

into  white  cast  iron  by  remelting.     B  is  malleable  263 

Fig.  124 — (Right) — Tobin  bronze  weld  in  malleable.  Note  absence 
of  oxides  and  slag  in  weld  and  absence  of  recombination  of 
carbon  due  to  relatively  low  melting  point  of  breeze.  A  is  . 

bronze,  B  is  malleable   263 

Fig.    125 — Analytical    laboratory    in    malleable    plant    268 

Fig.    126 — Apparatus    for   determining   carbon    269 

Fig.    127 — Inverted  types   of   metallographic   microscope    272 

Fig.    128 — Detail    of    inverted    type    of    metallographic    microscope 

(Bausch    &   Lomb)     272 

Fig.   129— A.   S.  T.   M.  tension  test  specimen    274 

Fig.    130 — Dimensions    of    proposed   tension   test  bar    276 

Fig.  131 — A  200,000-pound  Olsen  universal  testing  machine   278 

Fig.  132 — Ewing-type  extensometer  for  determining  elongation  under 

load      ..."....      279 

Fig.  133 — Olsen-type  torsion  testing  machine   280 

Fig.   134 — Leeds  &  Northrup  Co.  apparatus   for  determining  critical 




points    by    Roberts-Austin    method     281 

Fig.   135 — Apparatus   for  measuring  magnetic   properties  of   metal..  281 

Fig.    136 — Farmer    fatigue   testing   machine    282 

Fig.    137 — Charpy  hammer   for   impact   tests    283 

Fig.    138— Brinell   hardness   tester    284 

Fig.    139 — Stress-strain    diagram    of    malleable    cast    iron    in    tension  289 
Fig.    140 — Tensile   strength    and   elongation    plotted    from    specimens 
submitted    by    members    of    American    Malleable    Castings    As- 
sociation   291 

Fig.   141 — Effect  of  carbon  on  tensile  properties  of  malleable  iron..  293 
Fig.  142 — Relation  between  tensile  strength  and  elongation  of  malle- 
able   cast    iron    295 

Fig.    143 — Comparison    of    tensile    properties    of    machined    and    cast 

specimens  of   equal  diameters    296 

Fig.    144 — Results   of   tests   on   specimens   not   machined    298 

Fig.    145— V  groove   in   bar    300 

Fig.   146 — Necked  specimens  of   steel    (left)    and  malleable    (right)  301 
Fig.    147 — Stress    strain    diagram    of    malleable    cast    iron    in    com- 
pression   304 

Fig.   148 — Malleable    (center)    and  cast  iron    (right)    in  compression 
each  specimen  before  testing  was  of  the  size  and  shape  shown 

at  the  left    305 

Fig.   149 — Diagram   of    stresses   in   cross   bending  of    malleable    iron  308 
Fig.  150 — Displacement  of  planes  by  linear  shear  and   (at  right)   by 

torsional    shear     310 

Fig.  151 — Stress  strain  diagram  of  malleable  cast  iron  in  torsion....  311 
Fig.    152 — Diagram    showing    factors    to    be    considered    in    deter- 
mining   torsion    stresses 312 

Fig.    153 — Effect    of    elongation    of    specimen    on    the   resistance    to 

dynamic    tensile    loads     319 

Fig.     154— Walker     test     wedges      321 

Fig.    155 — Behavior    of   malleable   iron   under    fatigue    as   a   rotating 

beam     322 

Fig.  156 — Separation  of  grains  by  repeated  cross  bendings    323 

Fig.  157 — Relation  between  Brinell  number  and  strength  of  malleable 

iron    specimens     325 

Fig.  158 — Graph  showing  comparison  of  Brinell  and  Shore  numbers 

indicating  relation  between  them   is  not  definite    326 

Fig.    159 — Tests    of    machining    properties    of    malleable    cast    iron  330 

Fig.    160 — Graph    showing   values    of    a   in    drilling    formula    332 




Fig.   161 — Graph  showing  values  of'fc  in  drilling  formula    333 

Fig.    162 — Relation   of   torque   and   thrust  to   ultimate   strength    334 

Fig.    163 — Relation   of   torque  and   thrust  to  Brinell  number    335 

Fig.    164 — Slip   bands    in    ferrite    of    malleable    iron    341 

Fig.    165 — Intragranular   fracture   of    a   ferrite   grain   in   malleable..  342 

Fig.     166 — Intergranular     failure    of     malleable     343 

Fig.    167 — Ferrite   grains   in    malleable,    showing   slip   in   two    planes 

at     right     angles 344 

Fig.    168 — Slip   bands   due  to   plastic   compression    in   malleable    iron  345 

Fig.    169 — Plastic    deformation    of    malleable    in    compression    345 

Fig.   170. — Same   specimen   as   shown   in   Fig.    169    347 

Fig.    171 — Path    of    cross    bending    rupture    through    malleable    348 

Fig.    172 — Malleable    iron    compressed    about    one    half.      Annealed 

5  hours  at  650  degrees   Cent 349 

Fig.    173. — Stress    strain    diagram    of    malleable   iron    in   tension    for 

two   rates    of    loading 352 

Fig.  174 — Changes  of  strain  with  time  at  small  increments  of  stress  353 
Fig.  175 — Changes  of  strain  with  time  under  considerable  increment 

of   stress    (about   70  per   cent   of   ultimate   strength)     354 

Fig.  176 — Stress  strain  diagram  of  malleable  iron  in  repeated  tension 

under    increasing   loads    355 

Fig.  178 — Behavior  of  malleable  under  cyclic  cross  bending  at  con- 
stant   maximum    stress     358 

Fig.  179 — Maximum  deflection  and  permanent  set  under  cyclic  cross 

bending  at   constant   maximum    stress    359 

Fig.    180 — Stress    deflection   diagram    of   malleable   in   cross    bending 

with  and  without  previous   cold  work    362 

Fig.    181 — Effect   of    torsional    deformation    upon    subsequent    tensile 

strength   of    malleable    363 

Fig.    182 — Absorption  of   energy   from   successive   impacts    364 

Fig.    183 — Load   deformation   diagram   of    specimen   subjected   to   al- 
ternate   impact    , 367 

Fig.   184 — Magnetization   and  permeability  curves  of   malleable   cast 

iron .' 373 

Fig.    185 — Magnetic    properties    of    malleable    cast    iron    375 

Fig.    186 — Variation   of    electrical    resistance   of   malleable   cast    iron 

with     temperature 377 

Fig.  187 — Expansion  of  malleable  cast  iron   379 

Fig.  188 — Heat  transfer  from  machined  malleable  to  still  water  for 

various    temperature    differences     380 

Fig.    189— Effect    of    temperature    upon    tensile    properties    of    mal- 
leable  . 382 

Fig.  190 — Thermal  conductivity  of  malleable  cast  iron   383 


American  Malleable 
Cast  Iron 



SINCE  the  dawn  of  civilization  man  has  continuously 
labored  to  use  the  natural  resources  of  the  world  for 

his  own  well  being.  He  first  adapted  to  his  needs  the 
materials  most  easily  obtained  and  as  his  knowledge  and 
skill  grew  he  sought  to  find  or  make  other  materials  which 
would  better  suit  his  requirements. 

Copper  and  gold,  being  found  in  the  metallic  state  in 
nature,  were  the  first  metals  to  attract  his  attention.  More- 
over, being  malleable,  these  metals  were  readily  fashioned 
into  the  shapes  desired.  Far  beyond  even  legendary  his- 
tory the  mound  builders  used  copper  utensils  while  the  Incas 
and  Montezumas  used  gold  in  domestic  articles  as  well  as 
in  ornaments.  Of  the  various  metals  found  as  compounds  in  na- 
ture, lead,  silver  and  tin  are  fairly  easily  reduced  from  their 
ores ;  hence  prehistoric  metallurgists  soon  added  these  to 
the  list  of  available  materials.  Thus  the  age  of  copper  was 
succeeded  by  the  age  of  bronze. 

The  only  free  iron  found  in  nature  is  that  of  meteoric 
origin,  usually  existing  in  small  fragments  which  easily  rust 
away.  However,  in  a  few  cases,  notably  the  three  large 
siderites  brought  from  Greenland  by  Admiral  Peary  and 
now  in  the  American  Museum  of  Natural  History  in  New 
York,  meteoric  iron  has  been  put  to  industrial  use.  Peary's 
siderites,  which  are  the  largest  ever  discovered,  constituted 
the  only  source  of  iron  for  the  Esquimaux  of  northern 

Approximately  five  thousand  years  ago,  one  of  Pharoah's 

2  c   *"   AnteriCcirtm^M(ikletfble    Cast   Iron 

Courtesy  of  American  Museum  of  Natural  History 

Fig.    1 — A    meteorite    in    the    American    Museum    of    Natural    History, 
New    York,    brought   from    Greenland    by    Admiral    Peary 

masons  carelessly  left  one  of  his  tools  lying  on  the  masonry 
where  a  new  stone  was  being  set  in  building  the  pyramids. 
Thus  packed  in  lime,  this  earliest  known  piece  of  man-made 
iron  was  preserved  for  posterity.  The  method  doubtless 
used  by  the  Egyptian  iron  masters  still  persists  in  many 
semicivilized  communities. 

As  shown  in  Fig.  2  it  consisted  of  heating  rather  finely 
divided  ore  in  a  charcoal  fire  blown  by  a  hand  or  foot  bel- 
lows in  a  shallow  basin  in  the  ground.  The  charcoal  acted 
both  as  fuel  and  as  a  reducing  agent,  liberating  metallic  iron. 
The  temperature  being  low,  the  iron  did  not  combine  much 
with  the  carbon  nor  did  it  melt  freely.  The  pasty  bloom 
which  accumulated  in  the  hearth  was  removed  and  crudely 
hammered  into  the  desired  shape.  Obviously  the  process 
was  laborious,  yet  it  was  practiced  on  a  considerable  scale. 
It  is  believed  that  the  famous  pillar  of  Delhi  was  made  by 
welding  together  blooms  of  the  kind  just  described.  , 

Metal  of  this  kind  possessed  some  of  the  properties  of 
wrought  iron  or  unusually  soft  steel  of  the  present  day. 

Early  History  of  fronmaking 

However,  it  doubtless  was  variable  in  quality  since  the 
carbon  content  must  have  fluctuated  considerably  due  to 
the  changing  and  uncontrolled  temperature  conditions.  Not- 
withstanding this  lack  of  uniformity,  it  was  decidedly  a  bet- 
ter metal  for  tools  and  arms  than  the  copper  and  bronze 
preceding  it. 

Still  before  the  era  of  written  history  there  lived  a 
primitive  Carnegie  whose  very  name  has  been  lost.  This 
early  steel  master,  probably  a  native  of  Greece,  determined 
to  engage  in  the  quantity  production  of  iron.  He  substituted 
a  stack  or  shaft  for  the  shallow  hearth  then  in  use  with  the 
hope  of  rendering  the  operation  continuous  instead  of  in- 
termittent. He  introduced  blast  from  the  bellows  at  the 
bottom,  started  a  fire  of  charcoal  and  then  began  to  add 
alternate  layers  of  charcoal  and  ore  until  the  shaft  was  full. 
Presumably  he  expected  to  dig  out  blooms  of  iron  from  the 
bottom  of  the  furnace  at  frequent  intervals  and  to  supply 





Fig.  2 — A  primitive  furnace,   1500   B.   C.     The   illustration  was   repro- 
duced   from    an    Egyptian    wall    painting 

-•I ntcr icon    Malleable    Cast   Iron 

charcoal,  ore  and  air  continuously.  Doubtless  he  was  much 
surprised  when  on  some  occasion  instead  of  iron  blooms  ap- 
pearing, molten  metal  ran  from  the  opening  in  the  stack. 

Such  was  the  first  production  of  cast  iron.  The  better 
utilization  of  heat  in  the  shaft  furnace  had  produced  a  tem- 
perature high  enough  to  more  completely  carburize  the 
product.  The  decreased  melting  point,  coupled  with  the 
higher  temperature  reached,  produced  a  liquid  metal  prob- 

Fig.  3 — One  of  the  earliest  blast  furnaces 


ably  of  white  or  mottled  fracture.  Unconsciously  this 
primitive  artisan  discovered  the  blast  furnace.  Even  today 
the  process  of  smelting  iron  ore  is  governed  by  the  same 
general  principles  which  obtained  in  the  early  days  in  Greece. 
Only  the  technique  has  been  perfected. 

The  earliest  known  blast  furnace  purposely  to  make  pig  iron 
is  said  to  have  operated  in  the  Rhine  provinces  of  Germany 
in  1311.  The  industry  spread  over  the  rest  of  Europe  dur- 
ing the  succeeding  century. 

With   the   development  of   the   crude  blast   furnace,   one 

Early  History  of  Irontnaking 

of  which  is  illustrated  in  Fig.  3,  there  existed  two  kinds  of 
iron.  The  one  had  to  be  forged  to  shape  and  was  rather 
soft  although  not  easily  broken  and  the  other,  which  could 
be  cast  into  shape,  was  rather  hard  but  too  brittle  and 
fragile  to  use.  Obviously,  a  metal  of  either  of  these  limita- 
tions was  not  exactly  adapted  to  the  making  of  swords,  the 
manufacture  of  which  constituted  a  most  important  pro- 
fession in  the  early  days.  Therefore,  the  most  important 
metal  for  that  age  was  one  not  soft  enough  to  be  bent 
and  blunted  by  armor  nor  so  brittle  as  to  be  shattered  by 
a  sharp  blow.  In  the  search  for  a  material  to  better  meet 
the  requirements  of  the  armorer  some  pioneer  found  that  if 
the  soft  iron  produced  in  the  forge  were  heated  in  charcoal, 
the  surface  of  the  metal  could  be  made  harder — in  fact  the 
metal  could  be  hardened  throughout  if  the  treatment  were 
continued  long  enough.  It  was  learned  that  in  this  man- 
ner tools  and  weapons  could  be  produced  with  a  superior 

For  many  centuries  this  "blister"  or  cementation  steel 
was  the  only  steel  available.  One  of  its  principal  shortcom- 
ings was  its  lack  of  uniformity  across  the  section.  How- 
ever, this  was  later  overcome  by  remelting  the  carburized 
steel  in  crucibles,  thus  rendering  it  homogeneous.  The 
crucible  process  also  was  modified  by  melting  wrought  iron 
mixed  with  sufficient  charcoal  or  cast  iron  to  give  the  desired 
properties  to  the  metal.  The  amount  added  was  determined  em- 
pirically, for  at  that  time  chemical  control  from  the  viewpoint  of 
carbon  content  was  unkown. 

Thus  at  the  beginning  of  the  eighteenth  century  three 
kinds  of  iron  were  known  to  the  world.  These  were  wrought 
iron,  soft  and  worked  only  by  forging;  cast  iron,  brittle  and 
worked  by  casting;  and  crucible  or  cementation  steel,  some- 
times melted  in  the  process  of  manufacture  but  always 
forged  to  shape,  not  brittle  but  hard  enough  to  hold  an 
edge  and  be  tempered. 

Steel,  however,  could  only  be  made  from  wrought  iron, 
wrought  iron  only  from  ore,  and  neither  could  be  made 
from  the  relatively  cheap  cast  iron.  The  next  forward  step 
in  the  metallurgy  of  iron  and  in  fact  the  first  since  the  dark 

American   Malleable    Cast   Iron 

ages,  was  the  invention  by  Cort  of  the  puddling  furnace  for 
converting  molten  cast  iron  into  blooms  of  wrought  iron  by 
treatment  with  ore.  This  invention  made  possible  the  reduc- 
tion of  the  metal  from  its  ore  in  the  cheaply  and  efficiently 
operated  blast  furnace  and  its  later  conversion  into  mal- 
leable and  ductile  wrought  iron. 

Steel  was  sitill  made  by  using  wrought  iron,  now  ob- 
tained by  puddling,  as  the  raw  material.  This  continued 
to  be  the  only  source  of  steel  until  the  discovery  of  the 
bessemer  process  in  the  middle  of  the  nineteenth  century  and 
the  invention  of  the  open-hearth  furnace  by  Siemens  about 
15  years  later.  Both  of  these  processes,  which  depend  for 
their  success  on  the  increased  temperatures  available,  pro- 
duce liquid  steel  of  nearly  any  desired  carbon  content.  The 
former  process  uses  the  carbon  and  silicon  content  of  the 
molten  pig  iron  for  fuel,  burning  these  within  the  charge  by 
a  blast  of  air.  By  the  removal  of  the  carbon,  the  cast  iron 
becomes  steel  which  is  kept  liquid  by  the  heat  of  combus- 
tion of  the  carbon  and  silicon. 

Siemen's  was  practically  a  modified  reverberatory  fur- 
nace fired  by  gas,  the  fuel  and  air  for  combustion  being 
heated  in  regenerators  by  the  waste  heat  of  the  escaping 
products  of  combustion.  The  oxidation  *of  carbon  was  ac- 
complished, as  in  the  puddling  furnace,  by  the  oxygen  of 
the  hematite  iron  ore  added  to  the  slag.  The  essential  dif- 
ference between  Cort's  and  Siemen's  invention  was  that  the 
latter  worked  at  temperatures  sufficiently  high  to  keep  the 
resulting  product  molten. 

A  review  of  the  industrial  world  at  about  the  close  of  the 
American  civil  war  indicates  that  five  well  established  types  of 
iron  and  steel  were  being  used.  Charcoal  iron  was  made  directly 
from  ore  and  charcoal  on  the  same  principle  used  in  pre- 
historic "times.  This  material  resembled  wrought  iron  and 
was  practically  obsolete  from  a  production  viewpoint. 
Wrought  iron  was  made  from  cast  iron  in  the  puddling  fur- 
nace. It  was  a  pasty  mass  and  was  shaped  by  rolling  and 
hammering  only.  This  material  was  soft,  malleable  and 
ductile.  The  railroad  iron  of  which  the  MONITOR'S  armor 

Early  History  of  Ironmaking 

was  made  was  of  this  character.  A  third  material  was 
cast  iron  made  in  the  blast  furnace  and  cast  to  shape  in 
molds.  This  iron  was  incapable  of  being  bent  without 
breaking.  The  fourth  material  was  blister  or  cementation 
steel  made  from  wrought  iron  in  unimportant  amounts. 
This  steel  had  to  be  forged  to  the  shape  desired.  The 

Fig.  A — An  early  American  blast  furnace 

fifth  and  most  important  metal  was  steel  made  in  liquid 
form  by  the  crucible,  bessemer  or  open-hearth  process  from 
cast  iron.  This  had  so  high  a  melting  point  that  it 
was  incapable  of  casting  any  but  large  molds,  hence 
it  was  usually  cast  into  the  latter  form  and  rolled  or 
forged  to  shape.  When  desired  it  could  be  produced  of  a 
composition  permitting  of  hardening  and  tempering. 

A  sixth  product,  then  just  coming  into  use  is  the  subject  of 
this  volume. 

It  will  be  observed  that  in  none  of  the  first  five  products 
are  combined  the  properties  of  malleability  of  wrought  iron 
and  fusibility  as  found  in  cast  iron.  In  other  words,  no  ma- 
terial has  been  described  which  could  be  cast  into  intricate 

American    Malleable    Cast   Iron 



Early  History  of  Ironniaking  9 

shapes  and  which  would  be  in  any  degree  malleable  when 
complete.  The  problem  of  producing  a  malleable  cast  iron 
to  fulfill  these  requirements  had  long  occupied  the  minds  of 
the  iron  masters.  Since  Cort  had  produced  wrought  iron 
by  the  use  of  ore,  a  modification  of  his  process  which  would 
not  involve  the  melting  of  the  cast  iron  now  seems  to  us  a 
logical  conclusion.  In  1722  Reaumur,  a  French  physicist, 
described  a  process,  not  necessarily  original  with  him,  for 
producing  malleable  cast  iron  by  packing  small  castings  of 
(presumably  white)  cast  iron  in  pulverized  hematite  ore 
and  heating  them  to  bright  redness  for  many  days.  This 
method  evidently  was  suggested  by  the  cementation  process 
for  making  steel  from  wrought  iron,  substituting  for  the 
charcoal  which  adds  carbon  in  that  process,  ore  which  removed 
carbon,  the  same  reaction  later  discovered  by  Cort  as  applied  to 
molten  cast  iron. 

Reaumur's  discovery,  or  better  disclosure,  actually  grew 
into  an  industry  in  Europe.  It  happened  that  European 
white  cast  irons,  except  in  Sweden,  were  relatively  low  in  man- 
ganese and  high  in  sulphur,  owing  to  the  available  fuels  and  ores. 
Being  white,  it  also  was  low  in  silicon. 

Such  conditions  are  all  unfavorable  to  the  formation  of 
free  carbon  and  consequently  Reaumur's  reaction  was  never 
complicated  by  the  formation  of  temper  carbon  or  graphite. 
In  intention,  at  least,  the  annealing  removed  from  his  thin 
castings  all  the  carbon  which  burned  from  the  carbide  of 

The  amount  of  the  carbon  originally  present  was  im- 
material, in  any  event  the  resulting  casting,  if  the  anneal 
was  successful,  had  only  traces  of  carbon  but  contained  all 
the  other  chemical  elements  originally  present.  Having 
been  only  moderately  heated  it  retained  its  original  cast 
form  but  approximated  the  chemical  and  physical  properties 
of  wrought  iron.  The  shortcomings  arose  mainly  from  the 
fact  that  since  carbon  was  removed  through  the  surface, 
the  process  oould  not  be  commercially  applied  to  moderately 
thick  sections  owing  to  the  prohibitive  annealing  time. 
Moreover,  a  casting  having  both  thick  and  thin  parts  nat- 

American   Malleable    Cast   Iron 

Urally  would  be  completely  decarburized  in  the  former  while 
still  retaining  much  carbon  in  the  center  of  the  heavier  por- 
tions. If  the  process  were  continued  to  completion  in  the 
thick  sections,  trouble  from  oxidation  and  scaling  of  the 
thinner  parts  would  be  encountered.  Furthermore,  it  was 
difficult  to  be  sure  that  the  castings  were  annealed  clear 
through,  since  the  interior  is  not  available  for  inspection. 
Any  castings  not  annealed  through  would  be  brittle  owing 
to  the  remaining  undecarburized  core. 

Hatfield  in  his  "Cast  Iron  in  the  Light  of  Recent 
Research"  says  of  this  process  as  practiced  in  England  : 
"Essentially,  the  materials  used  in  Britain  in  the  production 
of  malleable  castings,  are  high  in  sulphur,  necessitating  a 
somewhat  lengthy  anneal  at  a  fairly  high  temperature  with 
a  view  to  annealing  largely  in  decarburization.  These  re- 
marks apply  also  to  the  practice  in  France,  Switzerland, 
Belgium  and  Germ.any." 

Production    of   "White   Heart"    Limited 

The  industry  thus  was  limited  to  comparatively  small 
tonnages  and  hence  to  crude  methods.  As  practiced  then, 
and  still  practiced  in  England,  Germany  and  France,  the 
product  is  used  largely  for  harness  parts  'and  small  and  un- 
important work.  Melting  is  frequently  done  on  a  small 
scale  either  in  crucibles  or  cupolas.  The  total  volume  of 
production  is  relatively  insignificant  in  the  iron  production 
of  Europe  aUhough  there  are  said  to  be  126  white  heart 
malleable  foundries  in  Great  Britain. 

Reaumur's  publication  was  productive  of  only  the  most 
meager  commercial  results  from  an  American  viewpoint. 
Boyden  and  his  immediate  successors  attempted  to  anneal 
by  decarburization.  The  metal  made  by  the  Philadelphia 
Hardware  and  Malleable  Iron  Works  before  the  Civil  war 
was  "white  heart",  as  was  that  of  at  least  a  number  of  its 
contemporaries.  About  1861,  however,  the  manufacture  of 
this  product  in  America  practically  ceased.  A  single  job- 
bing manufacturer  of  white  heart  malleable  continued  op- 
erations until  a  few  years  ago,  operating  largely  on  European 

Early  History  of  Ironmaking 

pig  iron.  At  least  one  plow  manufacturer  continues  to 
operate  on  the  basis  of  European  cupola  practice  and  to 
turn  out  white  heart  malleable  of  high  strength  and  low 

Many  of  the  stock  phrases  regarding  malleable  which 
have  gone  the  rounds  for  many  years  originated  with 
"white  heart"  metal.  For  instance,  the  fairly  widespread 
belief  that  malleablization  takes  place  from  the  surface  in, 
that  the  material  is  not  annealed  clear  through  and  that 
the  material  cannot  be  used  in  heavy  sections  because  of 
the  unannealed  center,  are  among  the  common  fallacies 
handed  down  from  Reaumur's  time.  Even  though  the 
"white  heart"  or  Reaumur's  process  never  has  possessed  any 
tonnage  significance  in  the  United  States,  and  has  been 
practically  discontinued  for  60  years,  its  faults  have  been 
frequently  assumed  to  apply  to  the  American  or  "black 
heart"  metal  by  those  not  conversant  with  the  facts. 

The  art  of  making  malleable  castings,  as  that  term  is 
understood  in  America,  was  discovered  probably  uncon- 
sciously by  Seth  Boyden  while  attempting  to  practice 
Reaumur's  method  in  Newark,  N.  J.,  in  1826. 

Boyden  was  a  manufacturer  rather  than  a  scientist. 
Probably  for  this  reason  no  formal  announcement  of  a  new 
discovery  was  made.  It  is  presumed  that  in  attempting  to 
duplicate  European  practice  with  American  pig  iron,  which 
is  low  in  sulphur  and  high  in  manganese,  he  inadvertently 
discovered  an  alloy  which  when  heated  to  produce  deear- 
burization,  graphitized  instead.  The  product  possessed  all 
the  properties  of  the  best  white  heart  metal  and  was  more 
easily  made  and  more  uniform.  Not  realizing  that  he  had 
discovered  a  new  art,  Boyden  continued  this  work  along 
the  lines  he  found  empirically  most  likely  of  success. 

Boyden  left  a  diary  covering  his  experiments  from 
July  4,  1826,  to  Sept.  1,  1832.  It  shows  that  he  was  at- 
tempting to  duplicate  Reaumur's  process.  Under  date  of 
Oct.  20,  1826,  he  writes  :  "I  have  a  piece  so  good  it  will 
not  harden  any  more  than  copper".  Yet  from  his  third  ex- 


American   Malleable    Cast   Iron 

Fig.  6 — Statue  of  Seth   Boyden,  erected  in  the  city  park  of   Newark 
N.  J.,  by  citizens   in  memory  of  the  man  who   laid  the  foun- 
dation   for    the    malleable    industry    in    the    United    States 

Early  History  of  Ironmaking 13 

periment  on  there  are  allusions  to  graphitization.  In  the 
report  on  the  third  experiment  he  states,  "Much  blacker  in- 
side and  not  half  so  good".  Again  in  Experiment  No.  5  he 
refers  to  a  piece  "which  had  been  done  totally  well  before 
rendering  dark  in  the  middle".  An  entry  on  the  eighth  ex- 
periment is:  "Quite  gray;  none  of  the  above  bend  or  are 
good  for  anything".  In  the  ninth  experiment  he  comments : 
"Hard  iron  melted  in  coal  dust  from  the  air  received  no 
change  but  in  scoria  and  coal  dust  became  soft  gray  iron. 
A  piece  of  Sterling  (grade  of  pig  iron)  without  W  (prob- 
ably wrought  iron)  in  soft  gray  state  done  (annealed)  eight 
times  remains  gray  and  unmalleable". 

Boyden  had  been  unconsciously  recording  the  first  ob- 
servation of  the  formation  of  temper  carbon  and  its  dis- 
tinction from  graphite.  Being  still  convinced  that  he  was 
striving  to  produce  a  steely  decarburized  iron  he  refers  in 
Experiment  No.  11  to  the  fact  that  "the  iron  was  tough 
when  broken  and  was  rather  too  dark  in  color".  Yet  in  the 
next  experiment  he  writes,  "Experiment  in  the  foundry. 
Sterling  the  toughest  but  very  dark.  Sprues  and  Sterling 
dark  and  good".  On  Sept.  10,  1826,  he  notes  that  "some 
of  the  pieces  were  tough,  gray  and  very  good".  On  Oct.  20 
of  the  same  year  he  makes  the  peculiar  observation  that 
"the  best  piece  I  have  ever  seen.... was  pale  blue  in  the 

For  many  years  neither  he  nor  his  successors  realized 
that  decarburization  was  not  essential  to  the  process.  He 
and  his  associates  laid  great  stress  on  packing  materials  and 
their  chemical  effect  upon  the  product. 

Inasmuch  as  the  graphitizing  reaction  discovered  by 
Boyden  forms  the  metallurgical  basis  of  the  present  indus- 
try, its  consideration  in  detail  will  be  reserved  for  a  later 
chapter.  Black  heart  or  American  malleable  cast  iron  bears 
no  metallurgical  relation  to  the  European  product  and  its 
history  begins  not  with  Reaumur  but  with  Seth  Boyden. 



SETH    BOYDEN    began   business    as   an    iron    founder    in 
1820   at   26   Orange   street,   Newark,    N.   J.      Being   inter- 
ested   in    malleable    castings,    he    attempted    to    duplicate 
European    practice    at    a    time    when    metallurgy    was    prac- 
tically unknown.     After  six  years  of  continuous   experiment 
he  succeeded  in  producing  malleable  castings,  but  not  of  the 
kind  he  attempted  to  make. 

Due  presumably  to  the  raw  material  available,  he  hit 
upon  the  practical  operation  of  the  graphitizing  anneal  and 
thus  founded  a  new  industry.  Boyden  operated  the  plant 
under  his  own  name  until  1835  when  it  became  known  as 
the  Boston  Malleable  Cast  Iron  and  Steel  Co.  The  foundry 
continued  under  this  management  for  two  years,  after  which 
it  was  operated  under  various  firm  names  by  Daniel  Condit, 
J.  H.  Barlow  and  others,  becoming  in  1907  the  Barlow 
Foundry  Co.  This  company  occupied  the  original  site  until 
May,  1914,  when  it  removed  to  another  location  and  the 
birthplace  of  black  heart  malleable  was  razed. 

Quite  naturally  the  early  development  of  the  industry 
centered  about  its  discoverer  and  its  birthplace.  At  one 
time  Newark  had  eight  malleable  foundries,  and  three  of 
Boyden's  brothers — Otis,  Alexander  and  Frank — engaged  in 
the  malleable  founder's  art.  Otis  operated  a  foundry  in 
Newark  from  1835  until  1837,  when  it  was  absorbed  by  the 
Boston  Malleable  Cast  Iron  &  Steel  Co.  Alexander  and 
Frank  engaged  in  the  business  in  East  Boston  during  the 
same  interval,  after  which  Alexander  was  employed  by 
Frederick  Fuller,  of  the  Easton  (Mass.)  Iron  Foundry,  es- 
tablished in  1752.  The  business  later  came  into  the  hands 
of  Daniel  Belcher  and  was  continued  by  his  descendents. 

Two  plants  were  started  in  Elizabethport  about  1840 
and  in  1841  David  Meeker  began  to  manufacture  malleable 


American   Malleable    Cast   Iron 












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Development   of  Malleable  Industry  17 

in    the    Hedenburgs    Works.      The    New    Jersey    Malleable 
was   founded   at   Newark   in    1841. 

The  information  regarding  the  activities  of  the  Boyden 
brothers  and  their  contemporaries  and  associates  is  derived 
from  a  paper  presented  before  the  Philadelphia  Foundry- 
men's  association  by  George  F.  Davis. 

It  would  be  exceedingly  interesting  to  trace  back  to  its 
beginnings  the  present,  highly  developed  industry.  Un- 
fortunately written  records  of  the  early  days  survive,  if  at 
all,  only  in  the  account  books  and  the  minutes  of  stock- 
holders' and  directors'  meetings  of  the  older  corporations. 
Such  records  are  not  open  to  public  scrutiny  and  therefore 
it  is  difficult  in  sketching  the  early  history  of  the  industry 
to  do  full  justice  to  all. 

The  writer  has  been  unable  to  trace  in  complete  detail 
the  early  history  of  the  industry,  other  .  than  through 
Boyden's  activities.  This  may  be  due  to  the  fact  that 
these  older  plants  did  not  survive  or  may  be  caused  by  in- 
adequate search.  It  seems  to  be  of  common  knowledge  that 
during  the  first  half  of  the  nineteenth  century,  a  number  of 
persons  entered  into  the  business,  the  plants  being  mainly 
located  in  New  England  and  New  York,  at  least  one  as  far 
west  as  Buffalo. 

Thomas  Devlin  has  informed  the  writer  that  when  the 
Philadelphia  Hardware  &  Malleable  Iron  Works,  now  the 
Thomas  Devlin  Mfg.  Co.,  was  'founded  in  1852,  the  com- 
pany officials  knew  of  the  existence  of  the  Westmoreland 
(N.  Y.)  Malleable  Works,  of  a  plant  in  Worcester,  Mass., 
and  also  of  the  M.  Greenwood  Co.,  of  Cincinnati,  which 
was  founded  in  or  possibly  before  1850  and  later  was  taken 
over  by  James  L.  Haven. 

In  the  early  fifties,  Isaac  Johnson  established  a  mal- 
leable foundry  at  Spuyten  Duyvil.  In  1872  he,  together 
with  J.  H.  Whittemore  of  NaugatUck  and  W.  S.  Nichols,  a 
brother-in-law  and  representative  of  Walter  Wood,  organ- 
ized the  Hoosick  Malleable  Iron  Works  at  Hoosick  Falls, 
New  York.  Some  years  later,  Johnson  also  organized  the 
malleable  plant  bearing  his  name  in  Indianapolis,  which  in 

18  American   Malleable    Cast   Iron 

1883   passed   into   the  control   of  the  group   which   later   be- 
came the  National   Malleable  Castings   Co. 

In  the  early  eighties,  the  Walter  Wood  Mowing  & 
Reaping  Machine  Co.  absorbed  the  Hoosick  Malleable  Iron 
Works,  enlarging  the  plant  from  time  to  time.  The  same 
organization  under  the  style  of  the  Walter  Wood  Har- 
vester Co.  started  the  business  in  St.  Paul  which,  after  a 
failure  during  the  panic  of  1893  and  one  or  two  changes  of 
ownership,  became  the  Northern  Malleable  Iron  Co.  under 
Frank  J.  Otis. 

Much  of  the  early  development  centered  in  New 
England,  particularly  in  the  state  of  Connecticut.  Among 
the  oldest  malleable  plants  is  what  is  now  the  Naugatuck 
works  of  the  Eastern  Malleable  Iron  Co.  at  Union  City. 
Here  the  development  work  of  J.  H.  Whittemore  and  B.  B. 
Tuttle  was  done  beginning  in  1858.  From  that  plant  and 
that  of  the  ^Bridgeport  Malleable  Iron  Co.  were  recruited 
many  of  the  executives  who  established  the  industry  in  the 
Middle  West. 

The  Naugatuck  and  Bridgeport  plants,  with  those  at 
Troy,  Wilmington  and  New  Britain  became  the  present 
Eastern  Malleable  Iron  Co.  At  a  later  date  the  village  of 
Hoosick  Falls,  N.  Y.,  also  sent  westward  a  group  of  mal- 
leable iron  foundrymen.  G.  H.  Thompson  went  to  Colum- 
bus, John  Haswell  to  Marion,  and  later  to  Dayton,  O. 
Sidney  Horsley,  superintendent  of  the  Northern  Malleable  Iron 
Co.,  and  others  also  graduated  from  Hoosick  Falls. 

In  1854  Duncan  Forbes,  a  Scotchman  who  had  previously 
resided  in  western  New  York,  removed  to  Rockford,  111.,  and 
with  his  son  Alexander  Duncan  Forbes,  established  a  gray 
iron  foundry.  In  1859  Forbes  installed  an  annealing  oven 
and  intermittently  produced  cupola  malleable  castings  in 
connection  with  the  production  of  gray  iron  stoves  which 
constituted  the  larger  part  of  this  business.  In  1864  the 
gray  iron  portion  of  the  business  was  definitely  abandoned 
in  favor  of  malleable  castings  alone. 

Duncan  Forbes,  the  first  manufacturer  of  malleable 
castings  west  of  Cincinnati,  died  in  1870.  The  business  was 

__ Development  of  Malleable  Industry 19 

continued  and  enlarged  by  others  of  his  family.  In  1890 
the  company  was  incorporated  as  the  Rockford  Malleable 
Iron  Works  and  in  1907  removed  to  a  new  location  in 
Rockford,  where  it  continues  to  be  operated  by  descendants 
of  the  original  founder. 

In  1866  Charles  Newbold  and  Peter  Loeb  started  a 
malleable  and  gray  iron  foundry  in  the  east  end  of  Day- 
ton, O.,  which  was  incorporated  as  the  Dayton  Malleable 
Iron  Co.  in  1869.  In  1872  the  business  was  removed  to  its 
present  location  on  West  Third  street/  and  from  time  to 
time  the  capital  stock  and  plant  equipment  were  increased. 

In  1916  the  plant  of  the  Ironton  Malleable  Iron  Co. 
was  purchased,  and  has  since  been  operated'  as  the  Ironton 
works  of  the  Dayton  Malleable  Iron  Co.  In  February,  1922, 
the  Dayton  Malleable  also  took  over  the  foundry  of  the  Timken 
Co.  at  Canton,  Ohio. 

In  August,  1868,  the  Cleveland  Malleable  Iron  Co. 
was  incorporated  and  in  1869  Alfred  A.  Pope  became  inter- 
ested in  the  business  and  immediately  thereafter  its  presi- 
dent. In  1873  John  C.  Coonley,  sometime  of  Louisville, 
and  a  number  of  men  in  the  Cleveland  company,  started  the 
Chicago  Malleable  Iron  Co.  The  same  organization,  which 
in  1891  became  the  National  Malleable  Castings  Co.  ac- 
quired by  purchase  or  construction,  plants  in  Indianapolis, 
Toledo,  O.,  and  Cicero  and  East  St.  Louis,  111.,  besides 
steel  plants  whic'h  are  not  of  interest  in  the  present  con- 

A.  A.  Pope  and  J.  H.  Whittemore  were  leading  factors 
in  the  early  growth  of-  the  industry,  the  institutions  over 
which  they  presided  now  being  the  two  largest  in  the 
country.  Many  other  manufacturers  of  malleable  cast  iron 
have  honorable  histories  extending  back  into  the  sixties 
and  seventies  of  the  last  century.  The  writer  has  not  had 
the  opportunity  he  could  have  wished  to  do  full  justice  to 
the  histories  of  some  of  these  smaller  companies. 

The  industry  has  the  distinction  of  numbering  on  its 
rolls  a  president  of  the  United  States,  Mr.  Harding  having 
been  one  of  the  original  stockholders  of  the  American  Mai- 


American   Malleable    Cast   Iron 





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Development   of  Malleable  Industry  21 

leable  Castings  Co.,  organized  in  1905  under  the  leadership 
of  Charles  L.  LaMarche. 

In  this  as  in  other  industries,  the  growth  has  been 
largely  in  accord  with  the  survival  of  the  fittest.  Many 
plants  have  been  started  on  a  moderate  scale  especially  at 
times  of  great  industrial  activity.  Some  of  these  failed  to 
survive  the  first  period  of  depression  encountered ;  others, 
particularly  in  New  England,  continued  a  'small  but  often 
prosperous  existence,  catering  to  a  limited  trade,  usually  in 
their  immediate  neighborhoods.  A  number  of  the  organiza- 
tions grew  in  size  and  influence,  and  by  sound  business  and 
technical  methods,  coupled  with  an  aggressive  policy,  at- 
tained position  of  prominence  in  their  fields. 

Another  type  of  malleable  foundry  has  sprung  up  in  the 
history  of  the  industry.  This  is  the  foundry  which  pro- 
duces a  given  specialty  not  for  the  open  market  but  as  a 
department  of  an  organization  manufacturing  a  finished 
product.  Many  of  these  foundries  also  have  branched  out 
into  jobbing  work  when  not  fully  employed  for  their  own 
requirements,  but  are  primarily  operated  to  furnish  castings 
for  the  product  made  by  the  parent  company.  In  this  class 
are  the  malleable  foundries  of  the  General  Electric  Co,., 
American  Radiator  Co.,  International  Harvester  Co.  of 
America,  Ebefhard  Mfg.  Co.,  Link-Belt  Co.,  and  a  number 
of  others."  These  foundries,  having  a  definitely  established 
outlet  for  their  product  and  the  financial  and  administrative 
support  of  a  well  organized  industry,  usually  have  survived 
and  grown  successful.  However,  in  at  least  one  case  a  found- 
ry of  this  character  has  been  sold  to  a  malleable  founder 
in  pereference  to  its  continued  operation  by  the  consumer. 

The  organization  of  a  special  foundry  is  only  possible 
where  the  requirements  of  the  parent  company  run  up  to 
a  sufficient  tonnage  to  make  possible  operations  on  a  large 
enough  scale  to  warrant  the  best  operating  conditions  and 
supervision.  The  malleable  industry,  involving  more  expen- 
sive equipment  and  greater  technical  skill  than  the  gray 
iron  industry,  cannot  well  be  operated  in  small  units  on 
account  of  excessive  overhead.  Therefore,  unless  an  in- 
dustry is  large  enough  to  operate'quite  an  extensive  foundry, 


American   Malleable    Cast  Iron 

Development  of  Malleable  Industry  23 

castings    of    better    quality    usually    can    be    obtained    more 
cheaply   by   purchase   from    established   jobbing   foundries. 

The  present  extent  and  distribution  of  the  malleable 
industry  is  shown  in  Fig.  9.  Each  dot  on  this  map  repre- 
sents the  approximate  location  of  a  producer  of  malleable 
castings.  The  list"  is  as  complete  as  possible,  having  been 
compiled  from  the  data  of  the  American  Malleable  Cast- 
ings association  and  from  information  gathered  for  the 
government  during  the  war.  There  are  a  number  of  plants 
marked  as  producing  malleable  where  there  is  reason  to 
doubt  whether  they  have  actually  done  so.  The  most  recent  lists 
include  between  20  and  30  more  plants  than  are  shown  on  the 
map.  In  part  this  may  be  due  to  incomplete  returns,  and  to  a 
less  degree  to  new  foundries  of  very  small  capacity.  It  is  un- 
likely that  any  important  plant  has  been  omitted.  It  will  be 
noted  that  the  plants  are  largely  in  the  territory  north  of 
the  Ohio  and  east  of  the  Mississippi  rivers,  their  locations 
following  closely  the  various  divisions  of  the  Pennsylvania, 
New  York  Central  and  New  York,  New  Haven  and  Hart- 
ford lines,  with  an  additional  development  near  Milwaukee 
and  in  southern  Michigan.  These  locations  were  largely 
determined  by  the  fact  that  they  are  coincident  with  the 
important  manufacturing  districts  of  the  country,  present 
good  shipping  facilities  and  are  conveniently  near  the 
sources  of  fuel  and  pig  iron. 

A  more  interesting  compilation  from  the  viewpoint  of 
the  user  of  malleable  cast  iron  is  the  map  shown  in  Fig.  10, 
showing  the  principal  sellers  of  malleable  cast  iron.  This 
has  been  prepared  from  the  previous  map  by  the  elimination 
of  foundries  primarily  operated  as  departments  of  larger  in- 
dustries producing  finished  products,  as  for  example  harness 
parts,  pipe  fittings,  etc.,  and  of  foundries  whose  tonnage  is 
not  of  sufficient  magnitude  to  be  an  important  consideration 
from  the  viewpoint  of  the  consuming  interests.  It  will  be 
seen  that  the  distribution  is  almost  identical,  although  the 
number  of  plants  has  been  considerably  reduced. 

Annual    Production    of    Malleable 

The  plant  capacity  of  the  United  States  as  of  1920  is 
estimated  at  1,286,300  tons  annually,  divided  by  states  as 


American   Malleable    Cast   Iron 


Fig.  11— Comparison  of  production  of  steel  and  malleable  iron  castings 
in  the   United   States 

The  production  of  steel  castings  is  charted  from  the  statistics  compiled  by  the 
American  Iron  and  Steel  institute.  The  production  of  malleable  iron  castings  is 
carefuDy  estimated  on  the  basis  of  the  known  production  of  plants  whose  output 
constitutes  the  majority  of  the  annual  tonnage  of  the  country.  No  definite  figures 
ever  have  been  compiled  showing  the  actual  production  of  malleable  castings  and 
in  the  absence  of  such  information,  it  is  believed  that  the  above  charted  values  are 
as  accurate  as  any  that  can  be  obtained  under  existing  circumstances. 

follows:  Illinois,  297,700;  Ohio,  202,700;  New  York,  167,- 
500;  Pennsylvania,  133,100;  Wisconsin,  116,600;  Michigan, 
108,400;  Indiana,  88,300;  Connecticut,  58,200;  and  all  others, 

The  most  complete  information  at  the  writer's  disposal 
indicates  that  there  are  between  176  and  204  manufacturers  of 
malleable  castings  in  the  United  States.  In  this  list,  however,  are  in- 
cluded a  considerable  number  of  manufacturers  with  whom 
the  production  of  malleable  castings  is  only  incidental  to 
other  operations.  Some  of  these  produce  malleable  only 
intermittently  or  in  small  quantities,  as  their  own  need« 
require,  and  are  included  here  in  the  interest  of  complete- 
ness rather  than:  because  of  their  importance  to  the  job- 

Development  of  Malleable  Industry  25 

bing  trade.  About  85  per  cent  of  the  tonnage  of  the  country 
is  produced  by  76  manufacturers  having  a  capacity  in  ex- 
cess of  5000  tons  annually  each.  Sixty-two  and  one-half 
per  cent  is  produced  by  33  owners  having  capacities  over 
10,000  tons  per  annum.  No  single  manufacturer  can  be 
said  to  exercise  anything  approaching  a  monopoly,  as  the 
five  largest  interests  together  have  only  28  per  cent  of  the 
capacity  of  the  country.  Each  of  these  five  can  produce 
30,000  tons  per  annum  or  more.  The  eight  additional  manu- 
facturers, having  individual  capacities  from  20,000  to  30,000 
tons,  account  for  an  additional  14.2  per  cent. 

Data  as  to  the  production  of  malleable  castings  in  the 
United  States  go  back  only  to  1913  when  the  American 
Malleable  Castings  association  began  the  accumulation  of 
statistics  on  this  point.  Fig.  11  shows  the  production  of  mal- 
leable castings  by  years  since  1913,  compared  with  the 
production  of  steel  castings  by  years  since  1904,  as  recorded 
by  the  American  Iron  and  Steel  institute.  The  production 
of  malleable  pig  in  1913  was  about  5l/>  times  that  in  1900. 
This  would  imply  a  production  of  only  about  127,000  tons 
of  malleable  castings  in  that  year. 

It  will  be  noticed  that  the  annual  production  is  con- 
siderably below  the  annual  plant  capacity.  The  recent  fig- 
ures on  production  of  course  are  based  on  manufacturing 
operation  in  times  of  great  industrial  activity.  Under  these 
conditions,  a  deficit  in  production  compared  with  capacity 
seems  at  first  glance  unlikely.  This  deficit  is  due  to  two 
causes ;  first  the  fact  that  the  reported  capacities  are  doubt- 
less a  little  higher  than  the  facts  warrant  and  second  that 
most  of  the  malleable  foundries  had  been  unable  to  obtain 
either  sufficient  labor  or  fuel  to  permit  the  realization  of 
their  full  production.  In  other  words,  plants  apparently 
were  built  in  excess  of  the  available  labor  supply  and  no 
material  increase  in  the  country's  maximum  output  of  castings 
could  be  expected  as  a  consequence  of  the  erection  of  ad- 
ditional plants. 

In  view  of  the  lack  of  productivity  in  all  lines  of  manu- 
facture before  the  1921  depression,  it  is  unlikely  that  the  manpower 
of  this  or  any  other  industry  could  be  largely  increased  except  by 

26  American   Malleable    Cast   Iron 

increasing  the  productivity  of  the  individual  employe.  The 
only  visible  remedy  seems  to  be  an  increase  in  tonnage  per 
man  by  the  introduction  of  every  possible  mechanical  aid. 
A  considerable  improvement  may  be  possible  by  some 
means  tending  toward  a  decreased  loss  of  time  by  the  in- 
dividual worker,  and  an  increase  in  his  skill.  Data  based  on  con- 
ditions since  the  summer  of  1921  are  of  course  valueless  on 
account  of  the  very  small  production  in  all  lines. 

The  commercial  development  of  the  industry  was  par- 
alleled by  steady  progress  in  the  technical  details  of  malle- 
able production.  As  has  been  stated  earlier  in  the  discus- 
sion, Boyden's  discovery  was  not  the  result  of  a  logical 
metallurgical  development  but  was  the  accidental  outgrowth 
"of  an  attempt  to  practice  a  theoretically  distinct  art.  When 
it  is  realized  that  all  of  this  work  was  done  at  a  time  when 
even  the  chemical  analysis  of  iron  was  an  unusual  thing  and 
that  Boyden  and  his  successors  blazed  the  way  without  any 
knowledge  of  variations  in  raw  material  and  product,  save 
what  might  be  gathered  by  the  crudest  of  inspection,  we 
cannot  but  marvel  at  their  courage  and  persistence  in  estab- 
lishing the  empirical  basis  for  the  present  great  industry. 
Boyden,  however,  having  a  truly  technical  mind,  left  behind 
complete  notes  of  his  experiments  and  the  results  attained. 
Some  of  his  notes  already  have  been  quoted.  He  recog- 
nized the  presence  of  carbon  but  only  in  the  free  state,  be- 
lieving white  iron  to  contain  none.  He  made  many  experi- 
ments with  various  packings  and  under  different  annealing 
conditions,  finally  concluding  that  red  iron  ore  was  the  best 
material.  He  records  the  belief  that  the  annealing  temper- 
ature should  be  at  least  the  melting  point  of  silver.  He 
considered  the  presence  of  silicon  and  sulphur  but  knew 
nothing  of  analysis.  Under  date  of  Jan.  23,  1829,  he  records 
observations  as  to  the  effect  of  additions  of  phosphorus, 
clay,  lead,  zinc,  tin  and  antimony. 

Boyden's  brother,  Alexander,  seems  to  have  been  the 
earliest  mystery  monger  in  the  trade,  it  being  related  by 
Davis,  on  the  authority  XD£  Horace  Spaulding,  the  last  sur- 
vivor of  the  Easton  foundry,  that  Alexander  had  a  little 
pump  with  which  he  squirted  something  into  the  stack 

Development  of  Malleable  Industry  27 

and  also  that  he  used  to  throw  some  metal  into  the  furnace, 
creating  a  great  volume  of  smoke  and  doubtless  an  equally 
great  awe  in  the  mind  of  the  spectator. 

In  1872  Alfred  E.  Hammer,  of  the  Malleable  Iron  Fit- 
tings Co.,  began  to  study  the  chemistry  of  black  heart 
malleable  at  Branford,  Conn.  This  company  in  1864  had 
succeeded  to  the  business  of  an  earlier  one,  'the  Totoket 
Co.  founded  in  1854  for  the  purpose  of  practicing  Boyden's 

In  1875  Mr.  Hammer  had  established  a  chemical  lab- 
oratory which  was,  so  far  as  he  is  aware,  the  first  in  con- 
nection with  the  malleable  iron  industry.  Writing  of  this 
laboratory  he  says : 

"I  found  that  I  was  practically  in  an  unknown  country. 
For  that  reason,  'however,  the  work  was  not  only  interest- 
ing but  positively  exciting — so  much  so  that  I  had  a  mat- 
tress laid  in  my  laboratory  and  with  the  aid  of  an  alarm 
clock,  I  was  able  to  follow  the  then  tedious  chemical  oper- 
ations through  the  night  without  much  loss  of  sleep." 

As  a  result  of  this  work,  he  found  it  possible  to  lay 
down  "a  chemical  ratio  as  between  carbon  and  silicon,  and 
manganese  and  sulphur,"  thus  being  the  first  one  "to  bring 
the  malleable  process  down  to  a  chemical  proposition. " 

Among  Hammer's  difficulties,  not  the  least  was  that  at 
this  period,  pig  iron  was  not  made  and  sold  by  analysis. 
However,  he  soon  applied  his  chemical  ideas  to  the  selection 
and  mixing  of  irons,  irrespective  of  brands  and  grades. 

The  work  of  this  pioneer  metallurgist  seems  to  have 
escaped  adequate  recognition  since  his  conclusions  \vere 

thought  to  be  too  valuable"  trade"* secrets   to 'warrant  publi- 


He  certainly  came  to  correct  quantitative  conclusions 
as  to  manganese  and  sulphur  at  a  date  long  before  the  the- 
oretical explanation  was  even  thought  of.  His  views  as  to 
carbon  also  seem  to  have  been  far  in  advance  of  later  inves- 
tigators who  gained  much  greater  general  recognition. 

While  not  a  technically  trained  metallurgist,  A.  A. 
Pope  from  his  earliest  association,  with  the  industry  strove 
by  every  means  in  his  power  to  collect  and  interpret  ex- 


American    Malleable    Cast   Iron 

>       •*-> 

Development  of  Malleable  Industry 29 

perimental  data  bearing  on  the  processes  and  products  of 
his  plants.  These  investigations  were  conducted  by  Em- 
merton,  Benjamin  and  others  and  resulted  in  an  accumulation 
of  valuable  data  during  the  seventies  and  eighties. 

It  is  interesting  to  note  that  especially  with  reference 
to  manganese  and  sulphur,  Mr.  Pope's  conclusions  were  very 
similar  in  application  to  those  reached  at  about  the  same 
time  by  Mr.  Hammer. 

Among  the  most  progressive  of  the  malleable  manufac- 
turers was  the  late  B.  J.  Walker,  of  Erie,  Pa.,  who  pursued 
a  most  liberal  policy  with  regard  to  the  exchange  of  in- 
formation and  did  much  to  develop  the  industry. 

In  1893  McConway  &  Torley  established  in  Pittsburgh 
what  is  frequently  said  to  have  been  the  first  laboratory  in 
the  malleable  industry.  It  was  under  the  direction  of  Dr. 
Richard  Moldenke,  who  not  long  thereafter  severed  his 
connection  with  that  company  to  become  associated  with 
another  in  the  Pittsburgh  district.  H.  E.  Diller,  now  metal- 
lurgical editor  of  The  Foundry,  was  associated  with  Doctor 
Moldenke  at  this  time. 

In  the  autumn  of  1893,  James  Beckett,  after  a  tour 
covering  all  of  the  malleable  foundries  then  producing  agri- 
cultural implement  parts,  found  that  none  of  them  had  es- 
tablished a  chemical  laboratory  for  works  control.  This 
statement  does  not  apply  necessarily  to  plants  not  engag- 
ing primarily  in  this  specialty  which  were  not  visited  by 
Mr.  Beckett. 

In  1894  the  Wood  Mowing  &  Reaping  Machine  Co., 
Hoosick,  Falls,  N.  Y.  employed  Enrique  Touceda  as  a 
consultant  and  established  a  well  equipped  laboratory. 

In  1903  when  the  National  Malleable  Castings  Co., 
established  a  works  and  experimental  laboratory  at  Indian- 
apolis, the  author  was  unable  to  find  by  diligent  search  of 
the  literature  available  any  adequate  information  of  a 
definite  and  quantitative  character  regarding  the  chemical 
fundamentals  of  the  process.  Therefore  it  was  decided  to 
disregard  precedent  and  to  establish  a  sound  theoretical 
basis  for  works  control,  using  the  information  accumulated 
by  Mr.  Pope  as  a  nucleus.  In  this  connection  the  quantita- 

30  American   Malleable    Cast   Iron 

tive  effect  of  carbon,  a  sine  qua  non  in  the  works  control 
of  the  product,  was  worked  out  in  1904,  the  conclusion 
reached  being  apparently  new  to  a  number  of  the  best  in- 
formed malleable  men  with  whom  it  was  discussed  at  the 
time.  A  little  later  the  effect,  or  rather  lack  of  effect  of 
manganese  sulphide  was  also  worked  out.  This  offers  the 
theoretical  explanation  of  the  practical  observations  of  Mr. 
Hammer  and  Mr.  Pope. 

These  facts  were  certainly  discovered  independently  by 
other  observers,  including  W.  R.  Bean  now  of  the  Eastern 
Malleable  Iron  Co.  In  the  absence  of  contemporary  publi- 
cation it  is  impossible  to  state  whether  these  discoveries 
preceded  or  followed  the  Indianapolis  investigations.  So 
far  as  the  writer  has  been  able  to  learn  the  Indianapolis  laboratory 
was  the  first  to  successfully  exercise  complete  works  control 
on  the  basis  of  the  total  carbon  content  being  the  determin- 
ing factor  in  the  quality  of  the  product. 

During  all  of  this  time  the  results  of  none  of  these  in- 
vestigations became  publicly  available  and  therefore  it  is 
difficult  to  accurately  chronicle  the  scientific  development 
of  the  art.  The  organizations  collecting  scientific  and  re- 
search data  of  value  did  not  feel  it  to  be  sound  business  pol- 
icy to  make  public  disclosures  of  their  work.  Regardless 
of  whether  or  not  this  policy  was  fundamentally  sound  from 
the  manufacturers'  viewpoint,  it  certainly  proved  a  handi- 
cap to  the  consumer,  who  remained  in  ignorance  both  of  the 
theoretical  principles  and  practical  applications  of  the  manu- 
facture of  malleable  castings. 

Having  again  severed  his  business  connection  and  es- 
tablished himself  as  a  consultant.  Dr.  Moldenke  began  to 
contribute  voluminously  to  the  technical  press.  Unfortu- 
nately the  only  sources  of  information  open  to  him  seem  to 
have  been  the  work  in  which  he  personally  participated. 
Furthermore  he  was  presumably  handicapped  by  the  con- 
fidential character  of  his  relations  with  his  clients  and  ap- 
parently felt  constrained  to  speak  only  in  somewhat  gen- 
eral terms.  Nevertheless  he  did  yeoman  service  in  striving 
for  a  better  interchange  of  ideas  and  information,  and  also 
in  advocating  suitable  technical  control  of  the  industry. 

Development  of  Malleable  Industry 31 

His  services  in  this  direction  are  probably  of  even  greater 
importance  than  the  actual  informative  value  of  his  literary 
output.  The  earlier  literature  of  the  subject  was  derived  di- 
rectly or  indirectly  almost  entirely  from  his  publications. 

There  still  persisted  in  the  engineer's  handbooks  and  in 
the  technical  press  a  mass  of  ill-supported  conceptions 
largely  predicated  on  a  confusion  with  the  white  heart 
process.  For  example,  great  weight  was  attached  to  the 
oxidizing  action  of  the  packing  and  its  effect  on  the  proper- 
ties of  the  product  was  unduly  emphasized.  Great  dif- 
ferences also  were  supposed  to  exist  between  the  heart  and 
surface  of  the  same  casting.  Similarly  there  was  an  im- 
pression that  malleablizing  proceeded  from  the  surface  in- 
ward and  was  complete  at  the  surface  before  it  had  pro- 
gressed far  at  the  center.  A  corollary  to  this  belief  was 
that  very  thick  castings  could  not  be  annealed  clear  through. 

Since  none  of  those  who  knew  better  felt  called  upon 
to  publicly  combat  statements  of  this  character,  it  is  not 
surprising  that  the  engineering  public  was  left  in  ignorance 
and  hence  in  distrust  of  the  qualities  of  the  material.  More- 
over it  is  not  surprising  that  in  the  absence  of  guidance  by 
those  better  informed,  some  of  the  less  intelligent  and 
progressive  manufacturers  did  not  clearly  understand  the 
principles  of  the  process  they  practiced  and  therefore  pro- 
duced unsatisfactory  castings. 

A  few  of  the  larger  producers  maintained  adequate 
laboratory  facilities  to  investigate  and  control  their  methods. 
The  smaller  manufacturers,  however,  had  to  get  on  as  best 
they  could  with  their  own  resources  until  the  American 
Malleable  Castings  association  undertook  as  one  of  its  ac- 
tivities to  carry  on  extensive  research  work  for  the  benefit 
of  its  members.  Prof.  Enrique  Touceda,  of  Rensselaer 
Polytechnic  institute,  was  employed  as  consulting  engineer 
and  since  1913  has  labored  unceasingly  to  instruct  the  mem- 
bers of  the  association  in  sound  practice  and -correct  funda- 
mental principles.  This  work  was  largely  confidential  in 
character  and  added  little  to  the  user's  knowledge  but  con- 


American   Malleable   Cast   Iron 

Development  of  Malleable  Industry  33 

tributed    immensely    to    his    satisfaction    in    the    use    of    the 

At  about  this  time,  Oliver  Storey  published  the  results 
of  some  research  work  at  the  University  of  Wisconsin,  deal- 
ing with  the  fundamentals  of  the  graphitizing  reaction.  In 
the  writer's  opinion  this  was  the  first  scientific  American 
contribution  to  the  literature  of-  the  metallurgy  of  malleable 
iron.  The  problem  has  been  since  investigated  by  Archer 
and  White,  Merica  and  by  the  writer.  A  few  years  earlier, 
Hatfield  thoroughly  investigated  the  less  important  subject 
of  decarburization.  The  theoretical  aspects  of  graphitization 
have  been  studied  abroad  rather  thoroughly.  In  1881 
Forquignon  published  in  the  Annals  de  Chemie  et  de 
Physique  a  contribution  dealing  with  his  tests  in  the  an- 
nealing of  malleable  iron  and  steel.  Unfortunately  the  au- 
thor has  been  unable  to  familiarize  himself  with  this  pub- 
lication, which  is  said  to  have  dealt  very  adequately  with 
the  subject. 

In  1902  Charpy  and  Grenet  published  a  study  of  the 
graphitization  of  white  cast  iron  which  covers  the  ground 
very  fully  and  accurately,  even  in  the  light  of  present 
knowledge.  This  publication  seems  to  be  almost  if  not  en- 
tirely unknown  in  this  country.  Howe,  in  the  Transactions 
of  the  American  Institute  of  Mining  and  Metallurgical  En- 
gineers in  1908,  discussed  critically  and  exhaustively  the 
evidence  then  available  bearing  on  graphitization.  Hatfield 
in  1910  discussed  the  chemical  physics  of  the  precipitation 
of  free  carbon  from  iron  carbon  alloys  in  a  paper  before  the 
Royal  society.  In  1911  Rueff  and  Goecke  published  a 
study  of  the  solubility  of  carbon  in  iron  and  in  the  same 
year  Ruer  and  Iljin  discussed  the  stable  system  of  iron 
carbon.  Heyn  summarized  the  contemporary  knowledge  of 
the  iron  carbon  alloys  at  the  New  York  congress  of  the 
International  Society  for  Testing  Materials  in  1912.  That 
these  technical  investigations  have  been  of  so  little  service 
to  the  American  manufacturer  seems  a  reflection  upon  the 


American   Malleable   Cast  Iron 



I  js 

o      ^ 


Development  of  Malleable  Industry  35 

American   literature   of  the   subject  no  less   than  on   the   in- 
dustry as  a  whole. 

Honda  and  Murakami  in  the  Journal  of  the  Iron  and 
Steel  Institute,  of  Great  Britain,  (1920)  advanced  the  theory 
that  graphitization  does  not  take  place  directly  but  is  a 
consequence  of  oxidation  of  carbon  by  CO2  and  the  sub- 
sequent decomposition  of  CO  formed  with  liberation  of  free 
carbon.  In  the  light  of  his  present  knowledge,  the  author 
cannot  agree  with'  this  conclusion ;  nevertheless  it  is  a  most 
interesting  contribution  to  the  theory  of  the  subject. 

The  officers  of  the  malleable  association  soon  realized 
that  while  some  of  the  work  of  its  consulting  engineer  was 
properly  of  a  confidential  character,  there  existed  a  necessity 
for  the  publication  of  authoritative  information  regarding 
malleable  cast  iron.  Accordingly  the  association  encouraged 
participation  in  the  programs  of  the  technical  societies  by  its 
consulting  engineer  and  by  others  qualified  to  speak  on  the 
subject.  It  also  established  an  educational  committee  to  co- 
operate with  .institutions  of  learning  and  with  engineering 
organizations  in  the  dissemination  of  information  regarding 
the  product. 

Through  these  various  activities  a  fund  of  reliable  in- 
formation regarding  the  properties  of  a  well  made  product 
is  being  made  available  to  engineers.  The  cloud  of  mystery 
surrounding  the  manufacture  of  malleable  castings  is  being 
penetrated  and  the  conscientious  manufacturer  now  can  pro- 
duce reliable  metal  by  availing  himself  of  the  research  facil- 
ities offered  by  the  association. 

The  larger  manufacturers  have  found  it  desirable  to 
continue  research  departments  under  their  own  control  for 
the  investigation  of  their  individual  problems  and  for  the 
prosecution  of  research  in  subjects  beyond  the  scope-  of  the 
investigations  made  by  the  association. 

A  further  step  forward  in  the  industry  was  made  when 
the  American  Society  for  Testing  Materials  began  the  de- 

36  American   Malleable    Cast  Iron 

velopment  of  a  specification  for  malleable  cast  iron.  The 
first  specification  was  adopted  in  1904  in  a  perfunctory  man- 
ner and  apparently  was  dictated  by  a  single  individual.  This 
specification  lay  dormant  for  11  years  but  later  was  actively 
studied  and  revised  until  1919  when  it  assumed  its  present 
status.*  All  the  requirements  of  the  specification  now  in 
use  have  been  given  adequate  attention  by  a  well  informed 
and  competent  group  of  men  and  are  eminently  calculated 
to  safeguard  the  interests  of  the  consumer  without  being  an 
undue  burden  upon  the  producer.  It  may  be  assumed  that 
such  future  revisions  of  this  specification  will  be  made  as 
advancing  knowledge  and  new  requirements  may  warrant. 

The  necessities  of  the  war  also  served  as  a  great  stimulus 
in  this  as  in  other  industries.  The  limitations  of  labor  and 
fuel  and  the  exacting  requirements  of  war  material  forced 
the  attention  of  all  manufacturers  toward  a  closer  study  of 
their  operations  and  better  control  of  the  product. 

Probably  the  earliest  application  of  malleable  cast  iron 
was  in  the  manufacture  of  buckles  and  harness  parts.  This 
was  a  rather  natural  consequence  resulting  from  white  heart 
practice  where  only  thin  cross  sections  could  be  readily  de- 
carburized.  Subsequently  malleable  castings  for  wagon  and 
carriage  parts  were  produced,  and  as  the  design  of  agricul- 
tural implements  progressed  malleable  iron  was  the  major 
material  of  construction.  In  fact,  it  almost  can  be  said  that 
this  material  made  possible  the  production  of  agricultural 
implements  at  moderate  prices.  The  use  of  chain  belt  in 
implement  work  and  more  especially  the  invention  of  the 
Ewart  link  started  the  manufacture  of  malleable  chain  belt 
as  an  important  development  in  the  industry. 

The  railroads  also  became  important  users  of  mal- 
leable in  the  form  of  couplers  and  smaller  car  details.  For 
many  years  it  was  possible  to  divide  the  malleable  industry 
of  the  country  roughly  between  agricultural  implement  and 
railway  material  plants.  Indeed,  this  classification  still  sur- 

Tentative    changes    were    proposed    at    the     1922    meeting.       See 
Chap.  XIV. 

Development  of  Malleable  Industry  37 

vives  in  the  malleable  scrap  market.  Increasing  train  loads 
forced  the  abandonment  of  the  malleable  coupler  for  rail- 
way use  about  20  years  ago,  although  it  survives  on  certain 
mine  car  and  similar  equipment. 

There  remained,  however,  a  considerable  tonnage  of 
malleable  car  parts.  Influenced  partially  by  unfortunate  ex- 
periences with  foundries  selling  purely  on  a  price  basis,  and 
partly  by  the  introduction  of  the  steel  underframe  to  over- 
come difficulties  encountered  with  wooden  details,  the  mas- 
ter car  builders  restricted  the  use  of  malleable  so  that  the 
production  of  railway  malleable  rather  rapidly  decreased. 

Peculiarly  enough,  while  malleable  castings  were 
viewed  with  disfavor  by  the  car  builders,  practically  all  the 
standard  draft  gears  were  still  made  of  malleable  and  largely 
continue  to  be  made  of  that  product.  There  is  an  obvious 
contradiction,  for  the  draft  gear  not  only  is  of  vital  impor- 
tance but  is  subject  to  more  violent  stresses  than  any  other 
car  part.  This  is  explained  by  the  fact  that  in  general  the 
manufacturers  of  draft  rigging  dealt  with  competent  found- 
ries and  secured  a  uniformly  good  product.  By  tests  of 
their  output  they  assured  themselves  against  buying  and 
reselling  inferior  materials.  The  agricultural  implement 
trade  meanwhile  was  largely  withdrawn  from  the  open  mar- 
ket with  the  establishment  of  foundries  of  their  own  by  the 
International  Harvester  Co.  and  others. 

The  manufacture  of  malleable  pipe  fittings  also  has 
become  largely  the  business  of  plants  producing  the  finished 
product  instead  of  the  castings.  These  developments  and 
the  changed  industrial  conditions  of  the  last  seven  or  eight 
years  have  very  largely  altered  the  selling  field  for  mal- 
leable castings. 

The  handicap  under  which  the  railroads  operated,  in- 
volving curtailment  of  purchases,  for  a  time  reduced  them 
to  an  almost  negligible  factor  in  the  market,  although  jour- 
nal boxes,  car  wedges,  derailers,  draft  gears,  rail  anchors  and 
many  car  parts  now  are  made  of  malleable  cast  iron. 

_38 American  Malleable   Cast  Iron 

The  automobile  and  allied  industries  entered  the  field 
at  just  about  the  time  the  railroad  business  began  to 
wane,  and  are  among  the  heaviest  consumers  of  malleable 
castings.  The  applications  are  found  in  many  vital  de- 
tails as  in  rear  axles,  spring  shackles,  and  hubs,  as  well  as 
in  less  critical  parts  such  as  lamp  and  wind  shield  brackets 

Another  application  is  in  some  of  the  highest  grade 
electrical  starting  equipment  for  automotive  use. 

Applications  in  truck  and  tractor  design  of  similar 
character  have  been  made.  The  use  of  malleable  castings 
for  kitchen  ranges  has  also  become  standardized  in  the 
highest  grades  of  this  product.  In  hot  water  and  steam 
heating  systems  radiators  are  assembled  almost  exclusively 
by  the  use  of  one  of  three  types  of  malleable  nipples,  and 
malleable  pipe  fittings  are  standard. 

During  the  war  the  industry  was  kept  at  high  pitch  by 
the  exacting  requirements  of  the  allied  governments.  In 
addition  to  the  obvious  peacetime  applications,  such  as 
railway  equipment  and  automobile  parts  which  were  mere- 
ly increased  by  war  conditions,  several  entirely  new  uses 
were  developed. 

Among  the  applications  in  ordnance  material  were 
hand  and  rifle  grenades,  trench  mortar  shells  and  75-milli- 
meter shrapnel  noses.  The  air  service  required  fragmen- 
tation bombs  of  malleable  castings  and  the  tank  service 
equipment  and  artillery  tractors  developed  applications 
analogous  to  ordinary  automotive  equipment  but  involving 
greater  difficulty  in  manufacture. 

There  is  an  extremely  prevalent  impression  that  the 
manufacture  of  woodworking  and  other  cutting  tools  of  mal- 
leable iron  is  a  common  commercial  practice  and  that  the 
resulting  product  masquerades  as  steel.  Some  material  of 
this  character  must  have  been  niade  in  times  gone  by,  al- 
though the  writer  in  18  years  of  rather  intimate  acquaintance 
with  the  product  of  the  largest  producer  and  a  fair  familiar- 

Development  of  Malleable  Industry  39 

ity  with  the  output  of  some  of  the  other  principal  manufac- 
turers has  never  seen  any  of  this  product.  A  well  known  con- 
sumer of  malleable  for  other  purposes  states  that  hatchets  con- 
tinue to  be  made  from  malleable  iron  by  at  least  two  important 

One  important  manufacturer  of  vises  is  a  large  con- 
sumer of  malleable  and  several  concerns  have  made  shear 
blades  to  which  steel  cutting  edges  are  welded.  This,  with 
some  business  in  the  form  of  small  hammers,  and  many 
wrenches,  seems  to  be  the  extent  of  tool  applications. 

Just  what  the  future  may  hold  in  store  can  hardly  be 
foretold.  The  trend  toward  a  critical  study  of  the  proper- 
ties of  all  materials  and  comparison  with  the  service  require- 
ments of  engineering  details  without  doubt  will  produce 
occasional  adjustment  of  the  present  conventional  designs. 

The  railroad  business  doubtless  is  destined  to  return  and 
the  automotive  applications  to  increase.  The  opportunities 
for  malleable  for  radiator  nipples,  pipe  fittings,  etc.,  where 
resistance  to  rust  and  to  shocks  is  the  determining  factor, 
are  great.  Applications  in  the  electromagnetic  field  also 
give  promise  of  a  bright  future.  This  is  equally  true  of 
agricultural  appliances,  although  carriages,  wagons  and  har- 
ness are  permanently  decreasing  as  the  automotive  appli- 
cations increase.  The  shipbuilding  field  also  holds  consid- 
erable possibilities. 

Foreign  Production  of  Malleable 

The  production  of  malleable  iron  in  the  Dominion  of 
Canada  is  of  fair  magnitude,  there  being  10  plants  having  in 
1920  a  production  of  about  30,000  tons  in  the  aggregate. 

In  Europe  the  black  heart  industry  seems  to  have  been 
limited  for  many  years  to  a  single  British  producer,  the 
Leys  Malleable  Castings  Co.,  which  began  the  manufacture 
of  black  heart  malleable  some  time  between  1878  and  1880, 
and  the  European  factories  of  the  International  Harvester 
Co.  and  the  American  Radiator  Co.  It  is  possible  that  rela- 
tively recently  other  plants  have  started  the  manufacture 
of  black  heart  malleables  in  England,  more  especially  during 

40  American   Malleable   Cast  Iron 

the  war  period.  It  has  been  said  that  some  ten  or  twelve 
plants  now  engage  in  that  operation,  but  the  author  has  so 
far  been  unable  to  obtain  data  as  to  tonnage  which  might 
serve  as  a  check  on  the  magnitude  of  the  British  industry. 
At  the  May  24,  1921,  meeting  of  the  British  Iron  Research 
association  Professor  Thomas  Turner  declared  that  the 
United  States  makes  10  times  the  number  of  malleable  cast- 
ings made  in  Great  Britain. 

Malleable  Industry  in  Europe  and  Asia 

The  author's  most  recent  information  regarding  the  mal- 
leable production  of  continental  Europe  is  derived  from 
conversation  with  Raymond  Gailly,  of  Gailly  Freres,  Charle- 
ville,  France.  According  to  M.  Gailly  at  present  there  is  no 
production  of  black  heart  malleable  in  France  or  Belgium. 
However,  many  small  and  medium  sized  plants  for  the  pro- 
duction of  the  European  type  of  product  are  being  devel- 
oped. In  the  larger  plants,  the  mechanical  equipment,  espe- 
cially for  sand  handling,  is  in  accord  with  the  most  ad- 
vanced practice. 

Lower  sulphur  metal  is  becoming  available,  and  an 
increasing  interest  in  the  American  process  is  developing. 
Marcel  Remy  of  Herstal,  near  Liege,  Belgium,  has  been  ac- 
tive in  an  attempt  to  organize  joint  action  by  French  and 
Belgian  foundries  toward  the  study  of  the  process,  having  in 
mind  the  introduction  of  the  American  product.  M.  Remy 
has  submitted  a  report  on  malleable  iron  to  an  association 
of"  founclrymen  at  Liege  which  briefly  summarizes  the  pres- 
ent state  of  the  art. 

Commander  Kawahigashi  of  the  Imperial  Japanese  navy 
advises  that  there  is  one  malleable  foundry  in  Japan  operat- 
ing on  European  principles  and  none  making  American 
malleable.  It  seems  probable  that  this  constitutes  the  ex- 
tent of  the  malleable  industry  of  Asia. 



A~,L,of    the    ferrous    materials   used   commercially    may   be 
considered  as  alloys  of   iron  and  carbon.   Their  proper- 
ties are  determined  primarily  by  the  character  of  the  in- 
dividual constituents  present.    The  possible  entities  or  materials 
present  in  commercial  iron  and  steel  are  as  follows : 

Ferritc — -Carbon  free  iron. 

Ccmcntite — Iron  carbide  having  the  formula  FezC. 

Austenite — A  solid  solution  of  iron  carbide  in  iron,  homo- 
geneous in  character  and  of  indefinite  carbon  content. 

Pearlite — A  mechanical  mixture  composed  of  alternate 
layers  of  cementite  and  ferrite  in  such  a  proportion  as  to  con- 
tain about  0.89  per  cent  carbon. 

Martcnsite,  troosite,  sorbitc,  etc — Various  intermediate  prod- 
ucts between  austenite  and  pearlite. 

^Graphite — Free  carbon  in  flat  crystalline  plates. 
Temper  carbon — Free  carbon  in  an  amorphous  condition. 

The  common  irons  of  commerce  are  all  composed  of  various 
combinations  of  these  ingredients,  thus: 

Wrought  iron  is  nearly  pure   ferrite. 

Cast  and  annealed  steel  is  ferrite  and  pearlite. 

Tool  steel  (0.90  per  cent  carbon)  when  annealed  is  prac- 
tically pure  pearlite. 

Steels  which  have  been  hardened  and  tempered  are  mar- 
tensite,  troostite  or  sorbite  with  or  without  the  presence  of 
excess  ferrite. 

White  cast  iron  is  pearlite  and  cementite,  as  are  also  the 
very  high  carbon  tool  steels  (over  0.90  per  cent  carbon)  when 

Gray  cast  iron  is  pearlite  and  graphite,  usually  containing 
also  more  or  less  ferrite  and  sometimes  cementite,  depending 
on  the  combined  carbon  content. 


American   Malleable   Cast  Iron 

Fig.    15 — Austenite  and    ledeburite    in   manganiferous    white    cast    iron 

Large    gray    areas,    austenite;    speckled    white    and    gray    areas,    ledeburite,    the 
eutectic  of  cementite  and  austenite 
Etched    with    picric    acid  x  2000 

Fig.    16 — Martensite   in   quenched   white   cast   iron   is    shown   by    inter- 
lacing   needle    structure 
Etched     with    picric    acid  x  2000 

Metallography  of  Malleable  Iron 


Fig.  17 — Troostite  in  steel.     The  dark  spots  are  troostite 

Etched    with    nitric    acid 

x  2000 

Fig.  18— Pearlite  in  incompletely  annealed  malleable 

Alternate    bands    of   ferrite    and    cementite    are    shown 
Etched    with    picric    acid  x  2000 


American   Malleable   Cast   Iron 

Fig.     19 — Spheroidized    pearlite 

Lamina    of    cementite    in    a    matrix    of    ferrite    are    shown,    the    lamina    being    in 
part  changing  to   globules   by   surface    tension 
Etched  with  picric  acid  x  4000,  but  reduced  one-half  in  reproduction 

Fig.    20 — Graphite    in    gray    iron 


Metallography  of  Malleable  Iron 


Fig.  21 — Soft  gray  cast  iron 

Black  represents  graphite  flakes,  the  white  areas  surroundng  the  black  are 
ferrite,  the  speckled  areas  are  iron  carbon  phosphorus  eutectic,  and  the  gray  areas 

Etched  with  picric  acid  x  20U 

Fig.  22 — Malleable  cast  iron 

The    black    represents    temper    carbon    nodules    and    the    white    ferrite 

x     200 

46  American   Malleable    Cast   Iron 

Malleable  cast  iron  is  ferrite  and  temper  carbon. 

It  will  be  noted  that  the  latter  product  differs  from  all  the 
others  in  containing  only  free  carbon  and  free  iron.  Further  it 
is  the  only  material  containing  temper  carbon  and  the  only 
cast  material  containing  ferrite  and  no  pearlite  or  other  form 
of  combined  carbon. 

It  owes  its  properties  to  this  combination  of  constituents, 
and  in  turn  it  owes  its  metallographic  composition  to  the  peculiar 
circumstances  under  which  it  is  produced.  In  this  case,  as  in 
all  others,  the  particular  metallographic  entities  present  are 
determined  by  the  chemical  composition  and  heat  treatment  of 
the  alloy. 

The  particular  substances  which  are  stable  at  different 
temperatures  and  concentrations  of  carbon  were  first  sys- 
tematically recorded  by  Roberts-Austin.  The  Roberts- Austin 
diagram  has  since  been  modified  in  accord  with  later  and  more 
accurate  quantitative  observations,  and  in  the  light  of  new 
knowledge  by  many  contributors. 

It  can  be  shown  that  there  are  two  typically  distinct  series 
of  alloys.  In  one,  cementite  and  iron  are  the  components 
present,  either  free  or  in  solution  in  each  other,  while  in  the 
second  free  carbon  enters  to  more  or  less  replace  the  carbon 
of  the  cementite.  On  the  basis  of  X-ray  spectrograms,  Jeffries 
and  Archer  have  concluded  that  cementite  itself  cannot  be  dis- 
solved in  solid  iron.  Alexander  has  taken  exception  to  this  rea- 
soning. Without  wishing  to  attempt  an  expression  of  opinion 
as  to  the  merits  of  the  controversy  in  a  field  with  which  he  is 
but  slightly  familiar  the  author  is  definitely  sure  that  two  dis- 
tinct types  of  solid  solutions  exist — one  of  or  in  equilibrium 
with  cementite  and  the  other  of  or  with  carbon. 

It  has  been  clearly  shown  by  Cesaro  that  molten  cast  iron  or 
steel  is  a  solution  of  cementite,  Fe.£,  in  iron,  Fe2.  Volumes  have 
been  written  to  prove  or  to  disprove  the  thesis  that  all  graphite  is 
derived  from  the  decomposition  of  solid,  or  frozen  cementite. 
However  this  may  be,  temper  carbon  is  always  a  decomposition 
product  of  previously  formed  cementite,  since  the  casting  before 
anneal  consists  only  of  cementite  and  pearlite. 

Metallography  of  Malleable  Iron 

20    %  CARBON 

Fig.   23 — Benedict's    diagram    recording   the    equilibrium    conditions    in 

terms    of    temperature    and    agraphic    (non    graphitic)    carbon. 

It   is    based   on    Benedict's    principle,    somewhat    modified 

In  this  case,  at  least,  we  may  base  our  conclusions  on  the 
conditions  as  outlined  by  the  Benedicks  in  the  form  of  a  double 
diagram.  Fig.  23  sums  up  the  principles  of  Benedick's  views 
with  sufficient  accuracy  for  the  present  purpose. 

In  this  diagram  the  absissae  or  horizontal  dimensions,  rep- 
resent carbon  content  in  per  cent,  the  ordinates  or  vertical 
dimensions  represent  temperatures  in  degrees  centigrade.  The 
conditions  of  equilibrium  are  then  represented  by  various  lines 
and  fields  on  the  diagram.  Thus  above  ABD  the  metal  is  a 
homogeneous  liquid.  A,BD  marks  the  relation  between  car- 
bon content  and  the  beginning  of  freezing,  while  AEBC  marks 
the  relation  of  carbon  content  and  completion  of  freezing.  In 
the  area  AEB  and  DBC  the  metal  consists  of  a  mixture  of 
homogeneous  liquid  and  theoretically  a  homogeneous  solid.  In 
the  former  area  the  solid  has  all  the  properties  usually  associat- 
ed with  a  solution  except  fluidity,  hence  the  term  'solid  solu- 

48  American   Malleable   Cast   Iron 

tion/  The  alloy  of  lowest  freezing-  point  B,  carbon  4.3  per  cent, 
is  known  as  the  eutectic  and  alloys  having  a  higher  carbon  con- 
tent than  E,  carbon  just  under  2  per  cent,  are  said  to  be  eutectif- 
erous,  that  is,  their  freezing  is  completed  by  the  solidification  of 
a  liquid  eutectic  at  constant  temperature  of  1130  degrees,  Cent. 
Davenport  has  pointed  out  that  the  massive  character  of  ce- 
mentite  in  commercial  white  cast  iron  is  an  evidence  of  super- 
cooling below  the  eutectic  freezing  point  followed  by  the  separa- 
tion of  pro-eutectic  cementite  in  addition  to  the  cementite  ot 
ledeburite.  This  point  is  of  interest  to  the  metallographer,  but 
may  be  disregarded  for  the  present  discussion.  The  solidifica- 
tion of  noneutectiferous  alloys  to  the  left  of  E  is  completed 
by  the  freezing  of  a  solid  solution  of  composition  dependent 
on  the  original  carbon  content  at  temperatures  marked  by  the 
line  AE.  Below  the  freezing  point,  other  rearrangements 
o£cur,  in  the  solid  metal. 

These  transformations  occur  at  definitely  fixed  temperatures 
dependent  on  carbon  concentration.  These  temperatures  are 
known  as  thermal  critical  points,  and  four  important  distinct 
critical  points  have  been  studied,  although  more  are  believed  to 
exist.  A  critical  point  is  marked  by  the  symbol  A.  The  four 
important  ones  are  distinguished  from  one  another  by  suffixes, 
the  points  being  named  Aif  A2)  Az  and  Acm.  The  numerals 
represent  their  relative  location  as  to  temperature,  Al  being  the 
lowest,  A3  the  highest.  Acm  is  not  strongly  marked  thermally, 
but  represents  the  solubility  above  A^  of  cementite  contracted  to 
cm.  Critical  points  vary  in  position  according  as  they  are  meas- 
ured on  a  rising  or  falling  temperature.  A  point  determined 
on  a  falling  temperature  has  the  letter  r  preceding  the  suffix, 
while  c  designates  a  critical  point  determined  on  a  rising  tem- 
perature. Thus  Ac^  is  the  lowest  critical  point  found  on  heat- 
ing from  room  temperature,  and  Art  the  same  point  as  de- 
termined in  cooling.  A  c  point  is  always  located  as  high  or 
higher  than  the  same  r  point  due  to  lag  phenomena.  The  des- 
ignations c  and  r  originated  as  the  initial  letter  of  the  French 
terms  for  heating  and  cooling.  The  A^  point  represents  the 
temperature  below  which  cementite  becomes  insoluble.  The  A2 
and  Az  points  represent  molecular  changes  within  the  iron  not 

Metallography  of  Malleable  Iron 49 

pertinent  to  our  present  discussion.  These  changes  are  called 
allotropic.  Incidentally,  however,  the  line  COS  marks  the 
minimum  solubility  of  cementite  in  the  solid  solution  or  perhaps 
better  the  maximum  solubility  of  iron  in  the  solid  solution. 
Alloys  below  and  to  the  left  of  this  line  are  mixtures  of  ferrite 
and  saturated  solid  solutions  Alloys  in  the  angle  GOSE  are 
homogeneous  solid  solutions  and  alloys  below  and  to  the  right 
of  ES  are  solid  solutions  mixed  with  cementite. 

For  a  full  discussion  of  the  iron  carbon  diagram,  which 
is  impossible  in  this  connection,  the  interested'  reader  is  referred 
to  Dr.  Howe's  monumental  work,  "The  Metallography  of 
Steel  and  Cast  Iron." 

The  exact  location  of  some  of  the  lines  has  been  ques- 
tioned on  the  basis  of  accuracy  of  observation.  The  solid  lines 
of  the  figure  indicate  the  equilibrium  conditions  in  the  metastable 
system  FezC — Fe. 

Freezing  of  White  Cast  Iron 

Confining  attention  to  that  area  between  the  values  carbon= 
2.00  per  cent  and  carbon— 3.00  per  cent,  marked  at  the  lower 
part  of  the  diagram  as  the  range  for  commercial  white  cast 
iron,  it  is  found  that  molten  iron  begins  to  freeze  when  it 
reaches  the  temperature  corresponding  to  the  intersection  of  the 
line  A  B  with  the  vertical  line  corresponding  to  its  carbon 
content.  Thus  for  a  carbon  content  of  2.50  per  cent  indicated 
by  the  line  x-x  on  the  diagram,  the  freezing  point  is  at  a. 
The  solid  material  is  lower  in  carbon  than  the  liquid  material 
remaining,  thus  at  a  temperature  b  the  alloy  x-x  has  a  solid 
phase  of  the  carbon  content  r  and  a  liquid  phase  of  the  carbon 
content  d.  At  the  temperature  e,  constant  for  all  alloys  of  more 
than  2  per  cent  total  carbon,  the  remaining  liquid  or  eutectic 
freezes  as  an  alloy  containing  4.3  per  cent  carbon.  The  solid 
formed  just  before  the  eutectic  freezes,  contains  about  2  per 
cent  of  combined  carbon.  In  freezing,  the  eutectic  breaks  up 
into  cementite  and  austenite  containing  2  per  cent  combined 
carbon  identical  with  the  solid  portion'  formed  just  before  the 
freezing  of  the  eutectic.  This  eutectic  when  frozen  is  known 
as  ledeburite. 

50  American   Malleable   Cast  Iron 

As  the  temperature  decreases  further,  austenite  is  saturated 
with  less  than  2  per  cent  combined  carbon,  the  solubility  de- 
creasing with  the  temperature  as  shown  by  the  line  E  S.  Thus 
when  the  alloy  x-x  is  at  the  temperature  /  it  consists  of  cementite 
and  a  decomposition  product  of  austenite  of  a  carbon  content '  g. 
When  the  temperature  falls  to  A±  at  the  point  h  the  solubility 
•  of  cementite  in  iron  becomes  nil  and  the  remaining  solid  solution 
then  containing  about  0.90  per  cent  carbon,  is  converted  into 
pearlite  consisting  of  a  mixture  of  cementite  and  ferrite  in 
such  proportion  as  to  give  a  carbon  content  of  0.90  per  cent. 
It  must  be  remembered  that  while  these  various  transformations 
of  the  solid  solution  are  going  on,  there  exists  also  the  cemen- 
tite formed  during  freezing  so  that  below  A±  the  metal  con- 
sists of  cementite,  pearlite  (cementite  +  ferrite)  and  the  socalled 
proeutectoid  cementite  separating  along  Acm.  This  is  the  actual 
course  of  events  during  the  freezing  of  the  ordinary  white  cast 
iron  of  the  malleable  industry. 

The  system  has  been  described  as  metastable,  in  other  words, 
it  is  permanent  as  regards  its  components,  not  because  actual 
final  equilibrium  has  been  attained  but  because  further  re- 
arrangement is  impossible  under  the  temperature  conditions 
obtaining.  If  the  iron  be  maintained  sufficiently  long  at  high 
temperature,  either  in  cooling  or  by  reheating,  the  cementite 
directly  or  indirectly  will  be  converted  into  free  carbon. 

This  reaction  is  due  to  the  fact  that  at  a  given  tempera- 
ture carbon  is  less  soluble  when  not  combined  with  iron  than 
in  the  form  of  Fe^C.  The  equilibrium  conditions  in  the  sLable 
system  Fe — C,  are  approximately  shown  by  the  dotted  lines. 
Ruef  and  Bowman  have  located  the  line  E'B'  at  1138  degrees 
Cent.  —  1  degree  (about  eight  degrees  above  the  eutectic  freez- 
ing point  of  the  metastable  alloys).  The  solubility  of  free  car- 
bon, as  distinguished  from  cementite  is  shown  by  the  line 
B'E'S'  although  there  is  room  for  argument  as  to  its  inter- 
section with  the  line  of  nil  carbon  content  and  with  A±  line. 
If  the  alloy  marked  xx  be  maintained  at  /  a  very  long  time, 
free  carbon  will  precipitate  and  cementite  dissolve  until  none  of 
the  latter  remains  and  the  system  consists  of  free  carbon  and  an 
alloy  having  an  agraphitic  (not  free)  carbon  content  /.  If  now 

Metallography  of  Malleable  Iron 


cooling  be  very  slow  the  carbon  can  be  progressively  precipi- 
tated with  decreasing  temperature  until  at,  or  about,  Alf  no 
agraphitic  carbon  will  remain.  Archer  maintains  the  solubility 
at  A!,  to  be  about  0.7 "per  cent  carbon  and  graphitization  to  be 
complete  below  that  point  only. 

Recent  work  under  the  writer's  supervision  by  Austin, 
Payne  and  Gorton  since  the  preceding  paragraphs  were  written 
has  demonstrated  the  existence  of  a  solid  solution  which  we 

f/?  Presence  OS* An  Ex- 
cess 0/* 

Fig.  24. — A   further  modification  of   Benedict's   diagram  indicating  the 
results    of    recent    research   work 

have  named  boydenite.  It  bears  the  same  relation  to  the 
stable  system  which  austenite,  in  its  generic  sense,  bears  to 
the  metastable.  Carbon  has  been  shown  to  have  a  defi- 
nite solubility  as  boydenite  immediately  above  Alt  confirming 
Archer's  views  as  to  the  existence  of  a  eutectoid  of  carbon  and 
iron.  The  relation  of  the  carbon  concentration  of  that  eutectoid 
as  now  determined  to  that  of  pearlite  is  contradictory  to 
Archer's  opinion.  The  solubility  of  carbon  in  boydenite  has  been 
accurately  determined  and  the  probable  locus  of  the  Alm  line 
E'S'  determined.  The  necessary  revisions  in  the  equilibrium 
diagram  are  shown  in  Fig.  24,  which  represents  the  best.informa- 

52 American  Malleable  Cast  Iron  

tion  now  at  hand  on  the  matter.  The  diagram  also  has  been  modi- 
fied to  take  cognizance  of  the  fact  that  the  alloys  are  not  binary 
but  ternary  containing  carbon,  silicon  and  iron.  The  liquidus  in- 
dicated is  derived  from  Gontermann's  data  interpreted  in  the 
light  of  additional  experiment  by  Hird  in  the  author's  laboratory. 

Graphite  and  Temper  Carbon 

Graphite  and  temper  carbon  are  chemically  identical  and 
differ  only  in  geometric  form.  Which  one  is  formed  depends 
only  upon  the  temperature  at  which  graphitization  occurs. 
lokiche  has  demonstrated  by  radiographic  means  that  their  crys- 
talline and  atomic  structure  is  identical.  If  carbon  forms  at 
a  temperature  near  the  eutectic  freezing  point,  hence  in  a  nearly 
liquid  medium,  it  can  spread  out  into  crystalline  flakes  of 
graphite.  If  it  is  formed  in  nearly  solid  iron  at  relatively 
low  temperature  it  remains  in  the  "amorphous"  temper  form. 

The  terms  "crystalline"  and  "amorphous"  in  this  connec- 
tion are  survivals  of  earlier  concepts  and  in  a  measure 
are  misleading  in  the  light  of  present  knowledge  of  what 
constitutes  crystallinity.  Temper  carbon  is  actually  possessed 
of  crystalline  structure,  i.  e.  orientation  of  its  atoms,  but 
has  not  grown  into  a  geometric  crystalline  form.  It  corres- 
ponds to  graphite  which  has  been  crushed  to  powder  and  bears 
the  same  relation  to  graphite  that  powdered  sugar  does  to  rock 

The  function  of  malleable  metallurgy  is  to  produce  a  gra- 
phite-free casting  and  then  graphitize  this  at  temperatures  such 
that  temper  carbon  results.  The  terms  "graphitize"  or  "graphitiza- 
tion" apply  to  the  separation  of  free  carbon  irrespective  of  its  geo- 
metric form. 

To  this  end  the  foundry  must  produce  a  white  cast  iron 
of  such  a  composition  as  to  be  readily  graphitized.  The  ten- 
dency to  graphitization  both  during  cooling  and  in  annealing 
is  affected  greatly  by  the  chemical  composition  of  the  product. 
Thus  silicon  and  some  of  the  rarer  elements,  notably  aluminum, 
promote  the  formation  of  the  stable  system  while  sulphur,  man- 
ganese, and  some  rarer  metals  retard  the  formation  of  the 
stable  system.  It  can  be  seen  that  the  properties  of  malleable 

Metallography  of  Malleable  Iron 53 

iron  depend  largely  on  the  total  carbon  present,  because  the 
more  carbon  is  present  the  more  will  the  ferrite  matrix,  of 
which  the  product  is  mainly  composed,  be  interrupted  by  that 
element.  Since  the  carbon  possesses  no  strength,  every  temper 
carbon  granule  decreases  by  that  much  the  strength  of  the 
product.  In  the  early  days  much  malleable  was  made  high  in 
carbon,  owing  to  the  advantage  of  a  lower  melting  point  with 
correspondingly  greater  fluidity.  At  times  the  carbon  was 
so  high,  as  compared  with  the  silicon,  that  some  graphite  formed 
in  freezing,  making  a  bad  matter  worse,  for  obviously,  a  thin 
flake  of  carbon  will  do  more  damage  than  a  spherical  nodule  of 
equal  weight.  From  this  practice  resulted  much  of  the  "rotten" 
iron  sold  10  years  ago.  Fig.  25  shows  such  a  metal,  in  which 
'  'primary"  graphite  present  in  the  original  hard  iron  persists 
unaltered  after  annealing  in  the  form  of  thin  flakes.  These  are 
located  between  ferrite  grains  and  cut  up  the  structure  badly. 

Use  of  Silicon 

Most  of  the  malleable  iron  made  by  the  better  manufac- 
turers today  ranges  from  2.30  to  2.70  per  cent  carbon  before 
annealing.  An  average  for  a  high  grade  product  in  castings  of 
fair  size  would  probably  be  between  2.40  and  2.50  per  cent. 
Small  work,  especially  where  the  highest  strength-  is  not  needed, 
still  is  often  made  of  higher  carbon  content,  even  up  to  3  per 
cent,  although  this  is  not  good  practice  from  the  viewpoint  of 
the  best  physical  properties.  Since  the  size  of  the  casting  affects 
the  rate  of  cooling  it  also  affects  the  tendency  to  graphitize  on 
freezing  and  hence  the  chemical  composition  required  to  pre- 
vent this  occurrence. 

Quite  generally,  this  tendency  is  held  in  check  by  controlling 
the  silicon  content.  When  little  or  no  silicon  is  present,  graphi- 
tization  in  the  annealing  process  is  retarded  to  a  commercially 
prohibitive  degree.  When  too  much  is  present  graphitization 
may  be  so  much  promoted  as  to  take  place  during  freezing. 
Most  classes  of  work  have  a  silicon  content  of  from  0.60  to 
0.80  per  cent. 

It  is  general  practice  and  sound  metallurgy  to  vary  the 
silicon  inversely  with  the  carbon  and  for  a  given  carbon,  in- 


American  Malleable   Cast  Iron 

Fig.    25 — Graphite    crystals    in    malleable    made    from    hard    iron    con- 
taining  graphite 

Black    grains    represent    temper    carbon  ;    heavy    black    lines,    graphite ;    thin    black 
lines,    grain   boundaries ;    white,   ferrite 
Etched    with    alcoholic    nitric    acid  x   100 

versely  with  the  cross  section  of  the  castings.  The  purpose  of 
this  practice  is  to  select  the  silicon  for  a  given  carbon  that  the 
castings  will  be  absolutely  free  from  graphite. 

For  rather  low  carbons,  say  between  2.10  and  2.40  per 
cent,  it  may  be  good  practice  to  let  the  silicon  vary  at  nearly 
the  same  rate  as  the  carbon.  For  instance,  2.40  carbon  and 
0.75  silicon  metal  has  practically  the  same  tendency  to  be 
graphitic  in  the  casting  or  to  mottle  as  2.10  carbon  and  1.05 
per  cent  silicon.  In  higher  ranges  of  carbon,  say  from  2.40 
to  2.80  per  cent  the  silicon  may  vary  only  three-fourths  as  fast 
as  the  carbon,  .2.80  carbon  and  0.45  silicon  corresponding  to 
2.40  and  0.75  per  cent  silicon. 

Extremely  Low  Silicon  Undesirable 

The  reduction  of  silicon  to  values  as  low  as  0.45  per  cent 
is  not  usually  good  foundry  practice  because  such  iron  is  easily 
oxidized  in  melting  and  produces  pin  holes  and  similar  diffi- 
culties due  to  the  liberation  of  carbon  monoxide  while  the  metal 

Metallography  of  Malleable  Iron  55 

Fig.  26 — Unannealed  hard  iron.     The  structure  is  always  dendritic  but 

varies    slightly    with   the   carbon   content 
White   is   cementite;   gray   is   pearlite. 
Etched    with    picric    acid  x  100 

is  freezing.  A  casting  which  would  prove  large  enough  to  re- 
quire the  carbon 'and  silicon  referred  to  above  probably  could 
not  be  successfully  made  with  less  than  0.55  or  0.60  per  cent 
silicon,  thus  setting  a  limit  for  maximum  carbon  distinct  from 
consideration  of  strength.  The  maintenance  of  proper  relation- 
ship between  carbon,  silicon  and  size  of  casting  is  usually  pos- 
sible only  on  the  basis  of  foundry  experience  and  constant  at- 
tention to  results ;  consequently  these  matters  cannot  be  briefly 
and  adequately  dealt  with  in  any  terms  of  general  application. 
From  the  consumers'  viewpoint,  any  attempt  to  embody  them 
in  specifications  would  be  the  height  of  folly,  because  the  prac- 
tice of  no  two  plants,  in  matters  of  casting  temperature,  sand 
preparation,  etc.,  would  be  nearly  enough  alike  to  make  any  one 
specification  generally  applicable  even  on  a  single  class  of  work. 
The  problem  would  be  further  complicated  by  variations  in 
the  size  of  castings.  The  figures  previously  given  may  be  un- 
derstood, to  apply  to  fairly  heavy  castings  and  represent  nearly 
minimum  values  of  silicon  for  a  given  carbon.  Light  work  may 


American   Malleable   Cast   Iron 

possibly  run  0.20  to  0.30  silicon  higher  and  unusually  small 
work  even  beyond  that.  On  such  extremely  light  work  the 
carbon  also  is  occasionally  well  above  2.80,  as  previously  ex- 
plained, sometimes  going  over  3  per  cent. 

It  is  not  necessary  to  lower  the  silicon  for  3  per  cent  carbon 

2J0      ^.00 

Fig.  27 — Effect   of  silicon   in   relation   to   carbon  on  malleable.     This 
graph   is    based   on   data    from    Thrasher's    determinations 

far  below  that  used  at  2.80,  partly  because  the  tendency  to 
mottle  in  very  high  carbon  alloys  is  relatively  little  affected  by 
the  silicon.  In  alloys  of  this  character  the  graphitization  ten- 
dency is  dependent  mainly  on  the  cooling  rate.  They  should 
never  be  used  in  metal  sections  of  any  thickness  since  their 

Metallography  of  Malleable  Iron 57 

freedom    from   graphite   is   dependent   primarily   on   their  rapid 

Sulphur  and  manganese  have  been  referred  to  as  opposing 
graphitization.  These  two  elements  unite  to  form  manganese 
sulphide.  This  compound  apparently  has  no  effect  on  the 
formation  of  temper  carbon.  Accordingly,  the  absolute  amounts 
of  the  two  elements  in  the  metal  are  unimportant  provided  they 
are  in  the  proper  proportion.  It  is  found  impracticable  to  fol- 
low the  theoretical  proportion  of  the  two  elements  exactly,  a 
slight  excess  in  manganese  always  being  necessary. 

Effect  of  Manganese  Sulphide 

A  low  sulphur  can  be  had  only  by  very  close  selections  of 
fuel  and  melting  stock  and  is  impossible  of  practical  attainment 
except  in  electric  furnace  practice.  The  low  manganese  re- 
quired for  low  sulphur  also  presents  difficulty  on  account  of  the 
manganese  content  of  the  available  ores.  The  presence  of  a 
moderate  amount  of  manganese  sulphide  does  no  harm  and  is 
sometimes  a  manufacturing  advantage.  The  user  need  there- 
fore have  no  fear  of  sulphur.  The  only  harm  this  element  can 
do  is  to  prevent  complete  graphitization  in  the  anneal.  A  physi- 
cal specification  for  tensile  properties  will  protect  the  consumer 
adequately  in  this  point  and  leave  the  foundryman  to  operate 
his  process  to  the  best  advantage  with  the  fuel  and  stock  avail- 

The  value  for  sulphur,  .06  per  cent  maximum,  written  into 
the  1904  specifications  of  the  American  Society  for  Testing 
Materials,  and  abandoned  at  its  first  revision,  is  particularly  ill 
founded  in  view  of  the  fact  that  very  little  malleable  is  made 
in  the  air  furnace  which  does  not  contain  about  that  amount 
before  annealing.  During  the  anneal  there  always  is  an  in- 
crease in  sulphur  ranging  from  0.005  to  0.03  per  cent.  It 
therefore  is  practically  impossible  to -produce  from  commercial 
raw  material  a  product  which  would  continuously  pass  this 
specification.  The  highest  grade  annealed  product  of  com- 
merce has  from  0.065  per  cent  to  0.10  per  cent  sulphur,  thus 
indicating  the  unsoundness  of  the  0.06  per  cent  limit. 


American    Malleable   Cast   Iron 

Fig.    28 — Beginning    of    graphitization    after    one    half    hour    at    1700 

degrees    Fahr. 

Black   represents  temper  carbon  ;    white,   cementite ;   gray,   martensite   to   sorbitic   mixed 
crystals.       Etched    with    picric    acid  x      100 

Fig.    29 — Progress    of    graphitization   after    ll/2  hours    at    1700    degrees 


Black  represents  temper  carbon;   white,  cementite;   gray,  martensite  to  sorbitic   mixed 

crystals.       Etched    with    picric    acid  x     100 

•  Metallography  of  Malleable  Iron    59 

Electric  furnace  metal  can  be  produced  as  low  as  0.01  per 
cent  sulphur  before  annealing.  The  application  of  the  desul- 
phurizing process  is  controlled  by  one  producer  through  the 
Kranz  patents.  No  particular  advantage  has  been  found  to  re- 
sult from  these  very  low  values  as  compared  with  slightly  higher 
amounts  and  the  triplex  process  usually  is  not  operated  to 
secure  desulphurization  to  a  point  below  0.04  per  cent. 

Phosphorus  also  has  been  regarded  with  more  fear  than  is 
warranted.  In  small  amounts  it  has  no  effect  on  the  product; 
for  example,  iron  containing  0.05  and  iron  with  0.15,  per  cent 
phosphorus  would  have  commercially  identical  properties. 

When  this  element  is  increased  to  about  0.25  per  cent  it 
no  longer  is  completely  soluble  in  the  ferrite  of  the  finished 
product.  It  then  has  a  direct  effect  on  the  properties  of  the 
metal.  In  this  respect  phosphorus  differs  from  all  the  other 
common  elements,  in  that  its  effect  is  not  due  to  its  action  on 
the  graphitizing  process. 

The  exact  point  where  phosphorus  begins  to  exert  a  harm- 
ful effect  depends  to  some  extent  on  the  heat  .treatment  em- 
ployed. Commercial  melting  stock  and  pig  iron  grading  are 
such  that  the  commercial  product  contains  from  0.15  to  0.20 
per  cent  of  the  element,  usually  about  0.18  or  0.19  per  cent, 
which  is  amply  safe. 

The  microstructure  of  the  unarinealed  product  is  practi- 
cally independent  of  chemical  composition,  unless  the  latter  be 
strikingly  abnormal.  The  structure  is  always  dendritic,  con- 
sisting of  hard  white  cementite  and  a  darker  ground  mass  of 
more  or  less  well  developed  pearlite,  as  shown  in  Fig.  26.  Of 
course,  there  are  miner  differences  of  structure  as  between 
different  samples,  lower  carbon  iron  containing  relatively  less 
cementite  and  higher  carbon  more.  The  coarseness  or  fineness 
of  crystalline  structure  is  dependent  upon  the  rate  of  freezing. 
In  very  rapidly  chilled  metal  it  may  happen  that  a  mesh  struc- 
ture is  substituted  for  the  dendritic.  This  condition  is  unusual 
in  castings. 


American   Malleable   Cast  Iron 

Fig.   30. — Progress   of  graphitizatoin  after  3^2  hours  at   1700  degrees 


Black  represents  temper  carbon ;   white,  cementite ;   gray,  martensite  to  sorbitic  mixed 

crystals.      Etched    with    picric    acid  x     10(1 

Fig.  31 — Equilibrium  at  1700  degrees   Fahr.  after  70  hours 

Black  represents  temper   carbon;    gray   and  white,   martensitic  mixed   crystals 
Etched    with    picric    acid  x     100 

Metallography  of  Malleable  Iron 61 

Turning  now  to  the  second  metallurgical  step  in  the  process, 
let  us  consider  the  changes  taking  place  during  graphitization 
in  the  so-called  annealing  of  castings. 

This  process  has  for  its  object,  not  the  elimination  of  car- 
bon as  many  appear  to  believe,  but  the  conversion  of  a 
metastable  alloy  containing  Fe3C  and  Fe  into  the  stable  system, 
consisting  only  of  Fe  and  C.  This  reaction  involves  no  changes 
of  the  ultimate  chemical  composition.  All  of  the  elements  re- 
main unaltered  in  quantity,  the  carbon  only  being  converted 
from  the  combined  to  the  free  state,  according  to  the  reaction, 

That  a  certain  amount  of  carbon  is  oxidized  is  a  mere  in- 
cident in  the  process.  The  elimination  of  carbon  is  of  prac- 
tical significance  but  is  not  in  any  sense  the  purpose  for  which 
the  annealing  operation  is  conducted.  In  this  theoretical  dis- 
cussion of  the  principles  of  malleable  iron  metallurgy  this  de- 
carburization  will  be  disregarded  and  only  the  essential  graphitiz- 
ing  reaction  will  be  considered. 

In  the  early  part  of  the  chapter  the  conversion  of  the 
metastable  into  the  stable  system  was  touched  upon  and  the 
mechanism  of  the  change  described.  The  equilibrium  in  the  lat- 
ter system  is  not  as  clearly  understood  as  that  of  the  former. 
This  is  due  largely  to  the  fact  that  steel  and  white  cast  iron 
furnish  commercially  important  examples  of  the  metastable 
system  in  which  equilibrium  frequently  is  attained.  Consequent- 
ly there  was  material  ready  to  hand  and  also  a  commercial 
necessity  for  the  study  of  the  system. 

Commercial  Application 

Malleable  cast  iron  furnishes  the  only  commercial  application 
of  material  involving  the  attainment  of  equilibrium  conditions 
in  the  stable  system.  .Because  the  output  of  malleable  is  small 
compared  with  that  of  steel  and  also  because  the  product  was 
not  always  known  and  understood,  even  by  the  more  progres- 
sive engineers,  the  theoretical  aspects  of  the  problems  of  mal- 
leable metallurgy  received  inadequate  attention  and  the  studies 
made  in  the  laboratories  of  some  of  the  universities  lacked  the 
advantage  of  contact  with  the  commercial  aspects  of  the  problem. 


.-hnerican   Malleable   Cast   Iron 

Fig.   32 — Imperfect  attainment  of  equilibrium  below  AI  due  to  too   short 

a    time 

Same  as  Fig.  31,  followed  by  three  hours  at  1200  degrees  Fahr.  Black  areas 
surrounded  by  white  represent  temper  carbon  ;  white,  ferrite  ;  gray,  pearlite. 
Etched  with  picric  acid  x  TOO 

Fig.    33 — Normal    malleable    iron,    metastable    equilibrium    below 

Black    represents    temper    carbon  ;    white    ierrite 
Etched   with  alcoholic   nitric  acid 

x   100 

Metallography  of  Malleable  Iron  63 

Significant  work  leading  toward  the  establishment  of  a  cor- 
rect equilibrium  diagram  for  the  system  Fe-C  was  done  by 
Storey  at  the  University  of  Wisconsin,  Archer  and  White  at 
Michigan  and  Merica  at  the  United  States  bureau  of  stand- 
ards. Howe  also  gave  adequate  attention  to  the  mechanism  of 
graphitization  in  his  "Metallography  of  Steel  and  Cast  Iron." 

It  has  been  pointed  out  a  number  of  times  in  this  text 
that  the  conversion  of  cementite  into  free  carbon  results  purely 
from  the  fact  that  the  solubility  of  carbon  in  the  stable  system 
is  less  than  in  the  metastable.  That  is,  solid  iron  will  dissolve 
less  free  carbon  than  carbon  in  the  form  of  iron  carbide. 

When  a  white  cast  iron  is  maintained  at  a  temperature 
higher  than  the  lower  critical  point,  Ac±  (1350  to  1400  degrees 
Fahr.)  free  carbon  is  slowly  formed  and  combined  carbon  is  re- 
duced to  a  corresponding  degree.  The  rate  at  which  this  change 
takes  place,  while  depending  upon  the  chemical  composition  of  the 
metal,  is  greater  the  higher  the  temperature.  However  for  each 
temperature  there  is  a  definite  value  of  combined  carbon  prac- 
tically independent  of  the  total  carbon  content,  when  the  re- 
action ceases  completely.  These  values  of  "combined"  carbon, 
measuring  the  solubility  of  carbon  as  distinguished  from  iron 
carbide  in  solid  iron,  have  for  their  locus  the  line  E'Sf  in  Fig.  24. 

The  word  "combined"  is  used  in  the  preceding  sentence  in 
what  may  be  a  somewhat  inaccurate  sense.  It  is  intended  to 
differentiate  free  carbon  from  carbon  which  is  not  in  the  free 
state.  Whether  the  combined  carbon  corresponding  to  the  line 
E'S'  is  actually  combined  with  iron  is  very  problematical.  Quite 
possibly  it  is  in  solid  solution  and  is  not  actually  combined  with 

Microstructure   of  Malleable 

Fig.  26  shows  the.  structure  of.  a  normal  piece  of  hard  iron 
as  cooled  in  the  mold.  When  white  cast  iron  is  raised  to  a 
temperature  well  above  the  Acl  point,  say  1700  degrees  Fahr., 
a  decrease  in  cementite  and  an  increase  in  the  constituent  forming 
the  gray  background,  called  "mix  crystal"  or  solid  solution, 
is  observed.  (See  Fig.  28.)  This  results  from  the  greater 
solubility  of  cementite  at  the  higher  temperature. 


American   Malleable   Cast  Iron 

Fig.    34— Graphite  crystals  produced  by  annealing  at  2100  degrees  Fahr. 

Black    represents    graphite;    white,    pearlite.       Unetched  x     100 

Fig.    35 — Manganese    sulphide    in      malleable    cast    iron.      The    arrows 

joint    to    MnS 

Etched    with    picric    acid  x     500 

Metallography  of  Malleable  Iron  65 

As  the  heating  at  1700  degrees  is  continued,  temper  carbon 
begins  to  form  at  the  expense  of  cementite,  as  shown  in  Figs. 
29  and  following,  and  finally  equilibrium  is  attained  by  the 
destruction  of  all  cementite.  The  structure  then  consists  of 
temper  carbon  and  solid  solution  of  carbon  in  iron,  as  shown 
in  Fig.  31  and  is  incapable  of  further  change  as  long  as  the  tem- 
perature remains  unchanged.  The  product  then  is  still  whitish 
in  fracture  and  very  brittle.  . 

If  the  temperature  is  allowed  to  decrease  the  solubility  of 
carbon  grows  less  and  more  temper  carbon  will  form  if  the  ma- 
terial is  held  sufficiently  long  at  the  lower  temperature.  How- 
ever, no  ferrite  will  be  formed  at  any  temperature  above  the 
critical  point.  The  ground  mass  above  this  point  will  remain  a 
homogeneous  .solid  solution,  differing  only  in  carbon  concentra- 
tion from  that  remaining  at  higher  temperatures. 

If  the  temperature  is  carried  down  to  1300  degrees,  that 
is,  below  Arlf  the  carbon  is  completely  insoluble,  though 
equilibrium  may  not  be  reached  unless  the  approach  to  this 
temperature  is  very  slow.  In  case  the  time  at  1300  degrees  is 
not  very  long,  a  structure  as  shown  in  Fig.  32  will  result,  con- 
sisting of  temper  carbon  surrounded  by  ferrite  which  in  turn 
has  a  background  of  still  incompletely  decomposed  mix  crystal 
persisting  from  the  higher  temperature.  At  temperatures  above 
the  critical  point,  this  ferrite  separation  does  not  occur,  the 
structure  strongly  resembling  Fig.  31,  except  as  to  detail  in  the 
metallic  matrix. 

Still  further  treatment  at  or  slightly  below  Ai\  will  result  in 
the  complete  graphitization  of  the  product  as  shown  in  Fig.  32 
which  represents  the  structure  of  malleable  cast  iron.  Accord- 
ing to  Archer's  views  as  to  the  solubility  of  carbon  at  A± 
graphitization  is  always  completed  only  by  treatment  below  A± 
as  outlined  above.  Graphitization  is  accomplished  commercially 
by  just  such  a  heat  treatment,  that  is,  by  heating  first  to  a 
fairly  high  temperature  for  a  considerable  period  and  then  cool- 
ing sufficiently  slowly  to  a  temperature  below  the  lower  critical 
point  of  the  stable  system. 

The  maximum  temperatures  and  time  chosen  are  largely  a 
matter  of  individual  judgment.  The  exact  location  of  this  line 


American   Malleable   Cast  Iron 

on  the  equilibrium  diagram  unfortunately  has  not  been  the 
subject  of  adequate  research.  Much  remains  to  be  done  in  map- 
ping its  course  exactly.  Our  last  knowledge  is  summarized  in  the 
revised  diagram  Fig.  24.  Since  there  is  no  microscopic  evidence 
of  an  iron  carbon  eutectoid  it  is  somewhat  doubtful  whether  Atrn 
should  be  interpreted  as  ending  at  S'  or  whether  there  is  a 
sharp  inflection  at  5',  Atm  running  nearly  parallel  to  A:  to  or 
toward  Pr .  The  significance  of  A2  and  As  in  the  stable  system 
has  so  far  eluded  experiment,  and  nothing  final  has  been  ac- 

I     I     I 

Diagramatic  Representat  on 


.._cti  _,.-..- 
inversion  in 

>ined  Carbon 






Time  Scale  Will  Depend  On  Chemical  Composition 

Fig.    36 — Chart   showing   conversion   of  combined   carbon    into   temper 


The  graphs  show  the  relation  between  the  carbon  remaining  combined  and  the 
lapse  of  time  at  each  of  five  temperatures.  Note  the  increasing  velocity  and 
higher  carbon  content  of  the  conclusion  at  high  temperatures  as  compared  with  low. 

complished  toward  the  location  of  5"'  as  affected  by  variations 
in  other  elements  than  carbon. 

These  points  are  of  very  great  academic  interest,  but  from 
an  operating  viewpoint  are  inconsequential.  No  operating 
errors  will  be  involved  in  considering  the  line  to  be  straight  and 
joining  the  two  points  mentioned. 

Fig.  36  showrs  in  diagrammatic  form  the  decrease  in  com- 

Metallography  of  Malleable  Iron  67 

bined  carbon  according  to  the  time  of  exposure  to  various 
temperatures.  It  will  be  noted  graphs  are  given  for  each- 'of 
a  number  of  temperatures.  The  horizontal  or  time  ordinates 
have  been  plotted  to  scale ;  however,  the  values  given  for  this 
dimension  are  suggestive  only,  since  the  rate  of  graphitization 
and  hence  the  time  to  attain  equilibrium  at  various  temperatures 
is  dependent  on  the  chemical  composition  with  respect  to  other 
elements  in  addition  to  carbon.  The  figure  is  given  as  an  ex- 
ample of  what  may  happen  rather  than  for  quantitative  inter- 

Speed  is  promoted  by  graphitizing  the  cementite  at  the 
highest  possible  temperature  but  to  a  certain  extent  at  the  ex- 
pense of  quality.  Temper  carbon  differs  from  graphite  only  in 
form.  It  has  been  pointed  out  that  these  differences  of  geo- 
metric form  are  due  to  the  temperature  of  the  metal  in  which 
the  free  carbon  is  formed.  Accordingly,  the  two  forms,  temper 
and  graphitic,  shade  over  into  each  other  by  infinitesimal  degrees 
and  the  temper  carbon  formed  at  high  temperatures  may  grow 
so  coarse  and  flaky  as  to  be  almost  graphitic.  Fig.  34  shows  the 
carbon  produced  by  graphitization  at  2100  degrees  Fahr.  far 
above  any  commercially  possible  temperature.  It  will  be  seen 
that  this  carbon  is  purely  graphitic  and  bears  no  resemblance 
to  the  temper  form.  Also  the  matrix  of  malleable  iron  is  not  a 
continuous  mass  but  consists  of  an  assemblage  of  individual 
grains  as  shown  in  Fig.  33.  The  character  and  size  of  this  grain 
structure  is  influenced  by  changes  of  heat  treatment,  introducing 
another  viewpoint  for  the  selection  of  annealing  temperatures. 
Moreover,  high  temperature  may  cause  operating  difficulties 
due  to  the  deformation  of  castings,  destruction  of  pots  and 
fusing  of  packing  material.  An  attempt  to  reduce  the  annealing 
period  too  far  by  a  rise  in  temperature  therefore  is  usually 

Commercial  practice  involves  a  maximum  temperature  of 
the  castings  of  between  1500  and  1800  degrees  Fahr.  The  time 
for  maintaining  the  maximum  temperature  varies  from  24  to 

American   Malleable   Cast  Iron 

60  hours,  or  even  longer,  the  longer  periods  properly  accompany- 
ing lower  temperatures.  The  commercial  rates  of  cooling  are 
variable,  ranging  from  5  to  12  degrees  per  hour. 

In  general  the  best  practice  is  opposed  to  the  highest  tem- 
peratures, the  minimum  time  of  holding  and  the  fastest  cooling 
and  favors  a  maximum  temperature  not  far  above  1600  degrees, 
a  time  not  less  than  40  hours  near  that  temperature,  and  an  aver- 
age cooling  rate  certainly  not  faster  than  10  degrees  per  hour; 
preferably  less,  more  particularly  near  the  critical  point. 

.When  properly  heat  treated,  malleable  cast  iron  contains  no 
combined  carbon  except  just  under  the  surface.-  It  is  prac- 
tically impossible  to  entirely  eliminate  these  last  traces  of 
pearlite  from  the  casting,  but  this  ingredient  can  and  should 
be  reduced  to  the  point  where  it  is  equivalent  to  not  more  than 
0.15  per  cent  of  combined  carbon  as  referred  to  the  total  weight 
of  the  casting. 

Approximately  six  years  ago  Thrasher  published  in 
graphic  form  the  relation  between  carbon  and  silicon  in 
while  iron  for  constant  tendencies  to  mottle.  Based  on  the  form 
of  Thrasher's  curves  and  known  points  near  the  middle  of  the 
range  of  composition  for  various  classes  of  work,  Fig.  27  has 
been  prepared  indicating  the  approximate  relation  between  car- 
bon and  silicon  for  various  classes  of  work,  based  on  the  ten- 
dency to  primary  graphitization  only. 

•  No  attention  has  been  given  to  the  weakening  effect  of  car- 
bon which  sets  limiting  values  on  that  element  nor  on  pouring 
temperatures  or  other  variables  which  may  affect  graphitization. 
The  data  presumably  apply  to  ordinary  air  furnace  practice  and 
doubtless  are  subject  to  a  certain  amount  of  modification  accord- 
ing to  other  variables. 

The  more  or  less  unavoidable  oxidizing  conditions  in  an- 
nealing remove  some  carbon  from  the  surface.  The  extreme  sur- 
face of  malleable  generally  contains  about  0.40  or  0.50  per  cent 
combined  carbon,  while  metal  more  than  0.1  -inch  below  the 

Metallography  of  Malleable  Iron 


surface  is  but  little  affected.  Malleable  castings  sampled  so  as 
to  include  no  material  less  than  1/8-inch  below  the  surface  will 
have  nearly  the  ultimate  composition  of  the  original  hard  iron, 
except  for  the  absence  of  combined  and  the  presence  of  free 
carbon.  If  the  sample  is  taken  to  include  the  entire  cross  sec- 
tion of  metal  the  total  carbon  will  vary  with  the  thickness  of 

Fig.    37 — Changes   of   metallographic    composition   during   the    freezing 
and    annealing    of    white    iron 

the  casting  and  will  range  from  0.40  per  'cent  or  even  less  up  to 
the  original  carbon  of  the  hard  iron.  In  Fig.  37  the  changes  in 
carbon  distribution  during  freezing  of  the  hard  iron  and  during 
its  subsequent  annealing  are  summarized  in  diagrammatic  form. 
Time  (estimated)  is  plotted  as  abscissae.  At  the  top  of  the 
diagram  the  assumed  temperature-time  curve  is  plotted.  At  the 
bottom  the  relative  weights  of  the  various  metallographic  en- 
tities are  recorded,  the  sum  of  course  always  being  100  per 
cent.  Along  the  middle  of  the  diagram  the  carbon  concen- 
tration of  the  various  homogeneous  solutions  (solid  and  liquid) 
is  plotted  for  convenient  reference. 



TODAY  all  malleable  foundries  in  the  United  States 
and  Canada  operate  upon  the  same  general  principles 
although,  of  course,  the  manner  of  execution  of  the  in- 
dividual operations  varies  with  the  ideas  of  the  individual 
operator  and  the  facilities  at  his  disposal. 

Physically  the  foundries  of  the  country  differ  widely 
both  in  size  and  type  of  buildings.  The  range  in  capacity 
of  plants  is  probably  from  50,000  tons  per  year  down  to  1000 
tons  or  less.  If  plants  making  malleable  only  as  a  side  issue 
are  included,  the  minimum  capacity  is  considerably  less  than 
1000  tons.  The  plants  range  from  antiquated  structures  of 
brick  with  low  wood  roofs  to  modern  brick,  concrete  and 
steel  buildings. 

A  similar  range  exists  in  the  facilities  available  in  the 
form  of  mechanical  equipment  and,  unfortunately,  also  in 
the  personnel.  It  does  not  necessarily  follow  that  the  larg- 
est production  is  coupled  with  the  best  buildings,  mechan- 
ism and  talent  although  in  this  as  in  other  industries,  many 
things  are  possible  for  the  large  operator  which  are  not  a- 
vailable  to  the  smaller.  Large  scale  operations  generally  in- 
volve conditions  better  suited  to  the  procurement  of  men 
and  machinery  of  the  highest  order. 

In  a  previous  chapter  there  have  been  outlined  the  prin- 
ciples upon  which  malleable  cast  iron  depends  for  its  proper- 
ties. It  was  there  shown  that  the  metal  is  the  product  of  two 
distinct  operations — the  making  of  castings  of  white  iron 
and  the  malleablizing  of  the  castings  by  a  subsequent  gra- 
phitizing  or  annealing  process.  This  divides  the  process  in- 
to two  distinct  stages  and,  generally,  the  plants  into  two 
separate  parts — the  foundry  and  the  annealing  departments. 

Centered  around  each  of  these  major  departments  are 
others  of  a  contributing  character  such  as  the  stockyard, 
mason's  department,  flask  shop,  patternshop,  coreroom,  melt- 
ing department,  and  chemical  laboratory  as  foundry  adjuncts 


American   Malleable    Cast   Iron 




General   Manufacturing    and    Plant  73 

and  cleaning,  trimming,  inspection  and  shipping  depart- 
ments, engineering  and  metallographic  laboratories  as  ad- 
juncts to  annealing.  Plant  maintenance  also  requires  the 
operation  of  a  power  station,  machine  shop,  electrical  de- 
partment, etc.  There  are  additional  departments  not  direct- 
ly of  a  manufacturing  character,  including  those  pertaining 
to  sales,  purchase,  accounting,  labor,  costs,  first  aid  and 

The  actual  shop  organization  by  which  the  departments 
are  subdivided  between  groups  of  executives  differs  widely 
in  different  companies.  Even  the  largest  producer,  operat- 
ing- seven  malleable  plants,  finds  it  wise  to  use  a  somewhat 
different  organization  scheme  in  each  of  its  foundries. 
Small  plants  usually  are  practically  "one-man"  shops.  One 
executive,  often  the  proprietor,  exercises  supervision  over 
all  works  activities.  The  scheme  is  simple,  but  incapable  of 
any  very  great  growth. 

A  common  method  is  to  divide  the  duties  among  three 
major  foremen  or  superintendents.  One  has  charge  of  the 
foundry  and  is  responsible  for  everything  up  to  the  delivery 
of  hard  castings  to  the  trimming  room;  another  converts 
these  into  the  finished  product;  and  the  third  is  in  charge 
of  power  plant,  carpenter,  machine  and  pattern  shops,  etc. 
Sometimes  the  last  two  are  co  ordinated  under  one  head, 
making  only  a  foundry  and  finishing  department.  A  much 
more  highly  organized  and  efficient  system  is  represented  in 
the  organization  chart  shown  in  Fig.  38,  which  is  applicable 
only  to  a  fairly  large  organization  and  incidentally  is  not 
exactly  followed  in  any  plant  of  which  the  writer  has 

The  raw  material  purchased  by  a  malleable  plant  con- 
sists of  pig  iron  and  scrap  as  melting  stock  ;  coal,  coke  and 
sometimes  oil,  gas  and  electric  power  as  fuel ;  molding  and 
core  sand  for  the  foundry  and  refractories  for  the  furnaces. 
In  addition  a  wide  variety  of  general  supplies  is  used  in 
more  limited  quantities. 

In  almost  all  plants  the  melting  operation  is  executed 
in  air  furnaces  which  generally  make  two  heats  a  day.  In 


American   Malleable    Cast   Iron 

K    *i-ir 

General   Manufacturing    and    Plant  75 

some  plants  only  one  heat  is  made  and  in  a  very  few  two  or 
three  heats  every  other  day  and  none  on  the  intervening  day. 
The  latter  practice  is  a  survival  of  a  practice  in  vogue  15 
or  20  years  ago.  Heats  vary  considerably  in  size.  On  a 
two-heat  a-day  basis,  they  vary  in  different  plants  from 
seven  tons  to  24  tons  each ;  on  a  one-heat  basis,  from  about 
18  to  35  tons,  and  on  a  three-heat  basis  from  five  to  10  tons. 

In  a  few  plants  the  cupola  is  employed  'for  melting  but 
this  practice  is  not  recommended  for  important  work.  Open- 
hearth  melting  has  been  tried  by  a  number  of  producers 
and  while  not  well  adapted  except  to  continuous  operation 
and  large  tonnages  is  in  successful  use  in  a  limited  number 
of  plants.  A  few  small  furnaces  each  having  a  capacity  of 
about  five  tons  are  said  to  have  been  tried.  The  charge  in 
most  successful  open-hearth  installations  averages  from  14 
to  20  tons. 

A  single  producer  operates  electric  furnaces  at  two 
different  plants.  From  10  to  12  heats  and  even  more  when 
molds  are  available,  are  'made  in  24  hours,  but  the  metal 
is  delivered  to  different  molders  so  that  generally  a  given 
molder  only  pours  off  twice  per  shift.  In  these  plants  heats 
range  from  five  to  seven  tons  and  from  eight  to  fifteen  tons 
in  weight  depending  on  furnace  capacity.  Six  and  twelve 
tons  are  the  nominal  furnace  capacities. 

Molding  still  is  done  by  hand  in  many  shops  as  it 
was  in  all  plants  15  years  ago.  The  patterns  being  small, 
many  are  mounted  on  a  single  gate.  The  pattern  is  pro- 
vided with  a  match  part  and  the  mold  made  in  a  snap  flask. 
Hand  operated  squeezers  'have  been  in  use  for  many  years, 
the  air-operated  devices  apparently  not  having  met  with 
general  favor,  although  used  in  some  plants. 

Recently  the  trend  has  been  strongly  toward  patterns 
mounted  on  plates  and  vibrated  by  air  when  the  cope  is 
being  lifted  or  the  pattern  drawn. 

In  many  localities  no  labor  now  is  available  capable 
of  commercially  producing  molds  fro'tn  other  than  plate  pat- 
terns. Consequently  this  form  of  mounting  which  requires 
less  skill  of  the  molder  than  any  other,  is  practically  forced 


Malleable    Cast    Iron 



General   Manufacturing    and    Plant  77 

on  the  industry.  Nearly  all  of  the  more  complicated  me- 
chanical devices  have  been  tried,  but  so  far  they  are  not 
used  extensively  except  for  floor  work,  in  which  case  various 
types  of  roll-over,  roll-over  drop  and  stripper  plate  ma- 
chines are  successfully  employed. 

As  already  stated  the  stna-le;  molds  are  usually  made 
in-  snap  flasks.  Sometimes,  when  there  is  clanger  of  breaking 
out  when  pouring,  the  molds  are  strengthened  with  mold 
bands  of  strap  ircn.  1  he  use  of  jackets  to  prevent  break- 
outs also  is  prevalent.  The  larger  molds  are  made  in  box 
flasks,  iron  flasks  being  very  common  and  desirable  for  use 
on  machines. 

All  malleable  castings  are  made  in  green  sand  except 
for  cored  holes.  Since  only  relatively  unskilled  help  is  avail- 
able, the  use  of  three-part  or  other  multiple-part  flasks  and 
loose  pieces  on  patterns  is  practically  impossible.  Any  pat- 
tern equipment  which  cannot  be  drawn  straight  out  or  rolled 
out  on  a  flask  hinge  is  incapable  of  quantity  production 
under  the  conditions  existing  in  most  foundry  centers. 

Cores  generally  are  made  of  local  sharp  or  lake  sands 
using  rosin,  oil  or  some  of  the  wood  sugars  as  binders.  As 
a  rule,  the  work  is  of  such  character  that  large  and  complex 
cores  are  not  required. 

A  few  foundries  are  beginning  to  prepare  and  deliver 
molding  sand  by  mechanical  means.  One  device  for  cutting 
sand  on  the  floor  is  coming  into  fairly  extended  use,  since 
human  sand  cutters  are  no  longer  available. 

Molds  are  commonly  set  on  the  floor  by  hand,  although 
at  least  two  semi-automatic  devices  for  removing' molds  have 
been  tried,  one  of  which  offers  prospects  of  successful  oper- 

No  methods  of  molding,  involving  successive  operations 
by  a  number  of  workers,  have  proved  entirely  successful 
thus  far.  Pouring  is  done  either  from  hand  ladles  or  from 
shank  or  "bull"  ladles  handled  by  two  men,  the  former  being 
more  common.  In  cupola  or  air  furnace  practice  molders 
catch  directly  from  the  stream  as  it  flows  from  the  furnace, 
the*  tap  hole  being  only  infrequently  closed  by  a  clay  stopper 
or  iron  bar. 


American   Malleable    Cast   Iron 


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General   Manufacturing    and    Plant  79 

In  electric  furnace  practice  and  sometimes  also  in  open- 
hearth  practice  the  heat  is  tapped  into  one  or  at  most  a  few 
large  crane  ladles.  Pouring  is  only  rarely  done  from  these 
ladles,  the  metal  being  transferred  to  hand  ladles  or  shank 
ladles  for  pouring  into  the  mold. 

For  relatively  heavy  work  the  metal  is  sometimes  re- 
moved from  air  furnaces  by  ladles  of  200  to  300-pounds  ca- 
pacity, mounted  on  two  wheels  and  pushed  and  tilted  by  one 
laborer.  These  so-called  "sulky"  ladles  can  be  used  to  pour 
work,  but  this  is  not  often  done. 

The  molds  are  shaken  out  by  laborers  who  also  re- 
move large  cores  and  break  off  the  gates.  This  is  easily 
possible  because  the  white  cast  iron  is  extremely  brittle ; 
indeed  great  care  must  be  exercised  to  avoid  accidental 

The  castings  are  usually  cleaned  in  tumbling  barrels, 
although  pickling  or  sand  blasting  is  sometimes  employed. 
The  cleaned  castings  are  inspected  and  gates  and  fins  are 
trimmed  off  with  light  hammers.  This  department  is  re- 
ferred to  as  the  trimming  room,  from  this  operation. 

Materials  for  Packing 

The  castings  then  go  to  the  annealing  department  where 
they  are  packed  into  pots,  either  with  or  without  packing, 
or  occasionally  stacked  directly  into  muffle  furnaces.  If 
stacked  in  pots,  the  pots  are  usually  introduced  into  the  an- 
nealing ovens  by  mechanically  operated  trucks. 

A  great  variety  of  materials  is  used  as  packing.  The 
original  process  was  thought  to  depend  on  the  use  of  hem- 
atite ore  for  this  purpose.  Later  on  "squeezer"  and  "roll" 
scale  from  puddling  mills  came  into  use  and  great  care  was 
exercised  to  keep  this  rusty  by  the  use  of  salamoniac  solu- 
tion. At  present  air  furnace  slag  is  the  commonest  ma- 
terial, although  blast  furnace  slag,  silicaquartz,  ground 
brick  and  many  other  materials  can  be  used.  A  refractory 
material  in  granular  form  to  support  the  castings  is  the  prin- 
cipal requirement.  Also  the  access  of  flame  to  the  castings 


4mcrican   Malleable   Cast   Iron 

=    2°. 

•~      £  t/T 

General   Manufacturing   and   Plant 

must  be   prevented   by   using  a   fairly   fine   packing  and   by 
keeping  the  pots  tightly  luted  with  clay. 

In  general  the  pots  are  from  15  to  18  inches  wide,  18  to 
24  inches  long  and  12  to  14  inches  'high,  being  approxi- 
mately rectangular  in  shape.  In  some  cases  the  size  of  the 
work  being  annealed  requires  pots  as  large  as  30  to  36 
inches.  Large  pots  usually  are  shallow  (about  6  inches 
high)  on  account  of  their  great  'weight.  A  larger  number 
of  pots  are  used  to  produce  the  desired  height  of  stack.  A 
few  plants  prefer  circular  pots  on  account  of  their  freedom 
from  distortion  under  heat.  This  advantage  is  offset  by 
their  being  uneconomical  of  floor  space  in  the  ovens.  The 
pots  have  neither  tops  nor  bottoms,  the  bottom  of  a  stack 
being  made  by  a  special  casting.  The  stack  of  bottoms  and 
pots  thus  forms  a  single  large  container. 


Annealing  ovens  vary  greatly  in  size  and  'hold  from  50 
to  350  pots  arranged  in  stacks  either  three  or  four  pots  high. 
The  largest  type  of  furnace  has  inside  floor  area  of 
about  625  square  feet  and  a  height  of  from  7  to  9  feet  to 
the  spring  line  of  the  arch.  Such  furnaces  obviously  hold 
enormous  tonnages  depending  largely  on  how  closely  the 
pot  space  can  be  occupied  by  castings.  Moderate  sized 
ovens  accommodate  about  15  tons  of  castings,  while  the  larg- 
est ovens  when  worked  to  full  capacity  can  handle  from  two 
to  four  times  as  much.  Some  small  commercial  furnaces  do 
not  hold  much  over  5  tons. 

Furnaces  generally  are  heated  with  coal,  fired  by  hand 
or  by  stoker  or  burned  in  pulverized  form.  Oil,  producer 
gas,  and  natural  gas  have  also  been  used  to  a  limited  degree. 

Continuous  furnaces  of  the  tunnel  kiln  type,  which  are 
just  coming  into  use,  seem  to  promise  great  advantages,  both 
economically  and  from  the  standpoint  of  control. 

While  the  heat  cycle  for  complete  graphitization  de- 
pends upon  certain  definite  scientific  facts  and  is  fixed  for 
a  given  class  of  material,  in  practice  the  cycle  is  also  de- 
pendent upon  the  firing  conditions,  the  circulation  of  gas 
in  the  furnace,  weight  of  furnace  contents,  etc.,  since  these 

82 American  Malleable   Cast  Iron 

affect  the  practical  means  for  attaining  the  desired  thermal 

Theoretically  the  cycle  can  be  reduced  to,  about  100 
hours  under  the  conditions  most  favorable  to  rapid  graphi- 
tization.  However,  the  production  of  the  highest  grade  of 
metal  under  operating  conditions  always  necessitates  a  cycle 
of  at  least  seven  days  even  under  conditions  most  favorable 
to  speed.  Cycles  of  12  to  14  days  are  not  uncommon  with 
large  furnaces. 

Incidentally  the  consumer  should  be  warned  against  a 
product  made  by  any  of  the  means  which  permit  of  cycles 
occupying  only  three  or  four  days.  Conditions  can  be  ar- 
ranged so  as  to  produce  merchantable  work  in  that  period ; 
in  fact,  the  writer  has  had  practical  experience  with  emer- 
gency annealing  intended  to  turn  out  two  charges  a  week 
from  a  'given  furnace,  and  actually  doing  so.  However,  the 
process  is  so  tricky  and  the  chance  of  inaccurate  control  so 
great  that  he  is  prepared  to  unqualifiedly  condemn  the  prac- 
tice. Furthermore  when  the  process  works  exactly  right  the 
conditions  are  such  as  to  preclude  the  use  of  sufficiently  low 
carbon  iron  to  produce  a  product  of  the  highest  quality. 

The  consumer  should  bear  in  mind  that  it  is  naturally 
to  the  manufacturer's  interest  to  use  the  shortest  practicable 
cycle  on  the  score  of  fuel  economy  and  decreased  overhead 
for  the  use  of  furnaces.  The  producer  therefore  requires  no 
outside  stimulus  to  hurry  this  portion  of  his  process  and 
such  a  stimulus  will  only  react  against  the  purchaser.  The 
conscientious  manufacturer  takes  sufficient  time  at  "a  cost 
to  himself,  in  order  to  produce  a  high  grade  of  work  and 
should  not  be  driven  from  this  laudable  position  by  the  ef- 
forts of  "stock  chasers"  whose  only  thought  is  of  quantity 
and  time. 

When  the  work  leaves  the  ovens  it  is  separated  from 
the  packing,  cleaned  by  rolling  or  sand  blasting,  subjected 
to  any  required  machining  or  grinding  operations,  inspected 
and  shipped.  These  operations  are  of  a  'general  character 
and  are  not  especially  characteristic  of  this  particular  in- 
dustry. Some  special  operations  will  be  discussed  in  detail 
later.  The  diagram  in  Fig.  43  summarizes  the  processes  by 

General   Manufacturing    and   Plant 


which  the  raw  material  is  trans  formed  intp  the  finished  cast- 
ings. It  is  evident  that  the  process  of  manufacture  is  so 
complex  that  the  cost  *of  operating  a  malleable  foundry  is 
much  greater  than  that  of  a  gray  iron  shop.  The  first  cost  of  a 
malleable  plant  of  given  capacity  greatly  exceeds  that  of  a  gray 
iron  foundry  of  the  same  size. 

The    foundry   buildings    and    operations   are    approximately 
identical   in   character   and   cost   with   tho.-e    for   gray   iron,    ex- 

Fig   43 — Chart    showing    cycle   of   principal   operations    in    a   malleable 


cept  that  the  cupola  is  a  cheaper  melting  apparatus,  usually 
in  operation  and  in  first  cost  than  any  of  its  competitors. 
When  a  gray  iron  casting  passes  the  trimming  room  it  is  in 
a  salable  condition,  except  for  some  additional  grinding.  A 
malleab1e  casting,  however,  still  has  to  be  packed,  annealed, 
cleaned  and  straightened.  In  this  process  over  half  as  much 
fuel  is  used,  in  many  plants,  as  was  used  in  the  original 
{netting.  The  overhead  also  is  burdensome  because  the  in- 


American   Malleable    Cast  Iron 

vestment  in  annealing  ovens  is  much  greater  per  unit  of  capacity 
than  the  investment  in  melting  equipment. 

The  division  of  labor  between  the  several  departments 
may  be  represented  with  some  pretense  at  accuracy  by  the 
diagram  shown  in  Fig.  44.  To  a  certain  extent  the  char- 
acter of  product  manufactured  alters  the  proportion  shown. 
For  example,  a  plant  making  small  castings  uses  fewer  la- 
borers per  molder  than  are  employed  in  making  heavy  cast- 
ings. Moreover,  in  a  plant  completely  developed  along  me- 

/io/der&  and 


Fig.   44 — Chart   showing  division  of  labor   in  a   typical   foundry 

chanical   lines,    the    ratio   of    unskilled  .to    skilled   men    and    of 
employes  to  product  is  greatly  reduced. 

It  has  been  estimated  from  data  gathered  for  use  of  the 
fuel  administration  during  the  war  that  the  country's  plant 
capacity  for  malleable  castings  was  about  1,000,000  tons  per 
annum,  and  the  labor  requirements  for  operation  at  capacity 
were  20,000  molders  and  coremakers  and  36,000  others.  This 
is  in  the  ratio  of  1.8  employes  other  than  coremakers  and 
molders  to  1  of  the  latter  group.  The  writer's  data  indicate 
a  ratio  of  about  2.2  to  1.  Both  sets  of  figures  are  based  on 
estimates  so  that  an  exact  agreement  is  impossible.  The 

General   Manufacturing    and   Plant 85 

government  estimate  indicates  further  that  the  production  of 
1000  tons  of  malleable  requires  the  employment  of  56  men 
for  one  year,  or  roughly  that  a  ton  of  malleable  represents 
a  labor  expenditure  of  about  155  hours.  In  the  writer's 
judgment  the  figure  is  probably  low  as  an  average  through- 
out the  country. 

The  amount  of  labor  involved  in  the  mere  handling  of 
material  mechanically  or  manually  in  a  foundry  is  seldom 
realized  by  those  not  conversant  with  the  trade. 

Conditions  vary,  o>f  course,  very  widely,  depending  on 
character  of  work,  plant  layout  and  so  on,  but  the  following 
table  may  be  regarded  as  suggestive  at  least  of  the  labor 
consumed  in  handling  material  for .  production  of  one  ton  of 
castings : 

Table  I 

No.  of 

Tons  of  times  Total  tons 

material  handled  handled 

Melting   stock    2.2  3  6.6 

Molten    metal    2.0  3  6.0 

Sprue    1.0  3  3.0 

Slag    1  6  .6 

Castings 1.0  19  19.0 

New  molding  sand 35  2  .7 

Used    molding    sand     5.0  25.0 

Core    materials     .25  10  2.5 

Fuel 1.2  3  5.1 

Cinders 175  2  .35 

Annealing  pots 1.5  6  9.0 

Packing     5  2.5 

Refractories 15  6  .9 

ll925  81.25 

Add    1/3   for    handling    supplies    and    equipment 27.08 


The  items  in  the  above  table  are  based  entirely  upon 
estimates.  The  writer  knows  of  no  attempt  to  actually  de- 
termine the  several  items.  Also,  evidently  the  expense  of 
handling  a  ton  of  material  can  have  no  unit  cost  assigned, 
for  the  term  "handling"  may  mean  picking  up  the  material 
and  transporting  it  by  a  crane;  picking  it  up  to  inspect, 
piece  by  piece,  or  the  laborious  operation  of  firing  a  ton  of 


American   Malleable    Cast   Iron 


General   Manufacturing   and   Plant  87 

coal  in  an  air  furnace,  or  wheeling  a  ton  of  sand  a  consid- 
erable distance  by  hand.  The  table  is  here  presented  pri- 
marily .to  show  the  importance  of  reducing  the  number  of 
handlings  each  material  undergoes  and  facilitating  each  by 
every  available  means. 

The  'history  of  labor  in  the  malleable  industry  has  been 
that  of  labor  in  all  similar  work.  In  the  early  days  the 
workers  were  practically  native  Americans,  supplemented  by 
thoroughly  Americanized  English,  Irish,  Germans  and  Scan- 
dinavians. Later  the  two  latter  groups  increased  consider- 
ably, and  still  later  toward  the  end  of  the  last  century  the 
influx  of  Balkan  immigration  began.  The  native  American 
and  the  original  foreign  'groups  meanwhile  drifted  almost 
entirely  out  of  the  labor  and  molding  groups,  though  a  few 
remain  principally  in  the  coremakers'  trade.  Most  of  these 
men  and  their  sons  headed  toward  the  machinists,  carpen- 
ters and  patternmakers'  trades,  or  toward  other  employment 
of  similar  character  but  requiring  less  skill. 

Type    of    Workmen    Available 

Meanwhile  the  Hungarians,  Bohemians,  Poles  and  Aus- 
trian-Slavs began  as  laborers  and  gradually  worked  upward 
through  the  various  grades  of  skill,  being  supplanted  in  the 
lower  grades  by  Italians  and  later  by  Bulgarians,  Greeks  and 
Russians,  and  still  later  by  Turks  and  Armenians.  In  some 
few  plants  the  negro  long  has  been  employed  in  all  but  the 
highest  skilled  trade1-  and  the  northward  migration  of  the 
southern  negro  farm  laborer  is  rapidly  enlarging  this  condi- 
tion. Postwar  developments  meanwhile  are  making  for  the 
return  of  many  former  subjects  of  Austro-Hungary,  Bulgaria 
and  Russia  to  their  native  lands.  He  were  a  rash  prophet 
who  would  attempt  to  discuss  the  net  effect  on  the  Amer- 
ican labor  market  of  this  emigration,  the  European  tendency 
toward  immigration  to  America,  the  discontent  of  those  who 
returned  to  Europe,  the  industrial  stagnation  of  Austria  and 
Russia,  all  in  the  light  of  the  American  immigration  laws 
and  shipping  facilities.  Natural  clannishness  of  foreign  races 
has  produced  a  segregation  of  nationalties  in  different  parts 

88  American   Malleable    Cast   Iron 

of  the  country.  The  lines  of  course  are  not  rigidly  drawn 
but  the  Scandinavian  still  persists  in  (the  northwest  and 
to  some  degree  in  the  St.  Louis  district.  In  the  terri- 
tory extending  from  St.  Louis  to  Terre  Haute  the  Armenian 
is  relatively  prevalent ;  the  Russian  and  the  Pole  have  set- 
tled in  the  Chicago  district,  as  also  the  older  class  of  Bo- 
hemians. The  region  around  Indianapolis  is  manned  by 
Greek,  Bulgarian  and  Austrian-Slav  foundry  workers,  while 
in  northern  Ohio  Poles,  Bohemians  and  Italians  dominate. 
The  latter  element  is  very  prevalent  through  the  Pittsburgh 
district  and  through  the  Shenango  and  Mahoning  valleys. 
New  England  and  New  York,  being  gateways  to  the  in- 
terior, probably  have  a  more  mixed  population  than  the  Mid- 
dle West. 

Foundries  of  all  kinds  have  been  confronted  with  these 
conditions :  First,  a  growing  disinclination  on  the  part  of 
all  labor  to  do  foundry  work;  second,  a  trend  toward  less 
and  less  skilled  and  intelligent  help;  third,  a  more  and  more 
turbulent  character  of  help  from  which  the  required  force 
must  be  recruited.  The  trend  toward  negro  labor  repre- 
sents a  turn  in  the  tide  at  least  in  the  latter  respect. 

The  industry  is  confronted  with  growing  labor  problems 
the  solution)  of  which  requires  the  best  efforts  of  its  ablest 
executives.  These  efforts  will  have  to  continue  for  a  long 
time  to  come  in  order  that  the  decreasing  productivity  of 
labor  may  be  prevented  from  being  reflected  in  the  product 
in  the  form  of  prohibitive  rates. 

The  solution  is  in  the  utilization  of  mechanical  aids  to 
the  utmost  and  in  an  enlightened  labor  policy. 

Metallurgy  of  Malleable  Is  Complicated 

Furthermore  the  malleable  process  is  metallurgically  more 
complicated'  than  that  of  either  gray  iron  or  steel  foundry 
practice,  and  the  chemical  range  consistent  with  good  results 
is  smaller  than  in  the  former. 

The  most  successful  means  of  overcoming  these  handi- 
caps in  manufacturing  cost  is  to  operate  upon  a  sufficiently 
large  scale  and  on  more  or  less  specialized  products  in  order 

General   Manufacturing    and   Plant  89 

to    take    advantage    of    those    manufacturing    economies    asso- 
ciated with  such  production  methods. 

By  inference  the  malleable  industry  is  not  well  fitted 
for  the  manufacture  of  so-called  short  orders,  that  is,  orders 
involving  only  a  few  pieces  from  a  given  pattern  and  small 
tonnages  for  a  given  consumer.  It  attains  its  greatest  suc- 
cess when  operating  on  orders  of  sufficient  magnitude  for  each 
type  of  casting  to  warrant  investment  in  the  best  possible 
pattern  equipment  and  close  study  of  each  step  in  the 



THE    raw    materials    of    the    malleable    industry    may    be 
classified    as    melting    stock,    fuel    and    refractories.      The 
remaining    materials    are    not    peculiar    to    the    malleable 
industry  and   therefore   are   not   important   in   the   present    dis- 

Regardless  of  what  melting  process  is  employed  in 
making  malleable,  the  melting  stock  is  selected  from  the 
same  general  classes  of  material.  Sprue,  which  includes 
the  feeders,  runners  and  defective  castings  produced  inci- 
dentally to  the  plant  operation,  is  seldom  if  ever  sold  and 
never  is  bought  by  a  malleable  foundry.  Being  a  product 
of  the  foundry-man's  own  plant,  its  composition  and  condi- 
tion are  known  to  him  and  the  material  requires  no  "further 

Malleable  scrap  is  a  material  derived  in  part  from  the 
work  condemned  at  the  plant  after  annealing.  Also  it  is 
an  article  of  commerce  in  the  form  of  scrap  material  con- 
sisting of  worn  out  malleable  parts.  The*  scrap  yard  of  a 
malleable  foundry  is  shown  in  Fig.  46.  Scrap  has  been  some- 
what roughly  divided  into  "railroad  malleable"  and  "agri- 
cultural malleable."  The  distinction  is  actually  one  based 
on  size  of  castings  rather  than  on  the  former  use.  "Auto- 
mobile malleable"  is  regarded  by  some  users  as  a  legiti- 
mate subdivision  but  really  does  not  differ  materially  from 
the  railway  malleable  scrap  from  a  metallurgical  standpoint. 
Pipe  fittings,  often  classed  separately,  could  equally  well  be 
included  with  agricultural  malleable  scrap. 

The  composition  of  purchased  malleable  of  course  is 
entirely  conjectural  and  there  is  therefore  a  limit  beyond 
which  its  use  introduces  serious  uncertainties  as  to  compo- 
sition of  charge.  It  is  safe  to  assume  that  railway  and  auto- 
mobile malleable,  before  annealing  had  a  carbon  content 


American   Malleable    Cast   Iron 


Melting  Stock  93 

averaging  about  2.50  per  cent.  No  two  pieces  are  alike  in 
carbon,  depending  both  on  the  original  carbon  and  the  de- 
gree of  decarburization  in  the  anneal,  but  the  remaining  car- 
bon in  work  of  these  heavier  classes  is  likely  to  be  around 
2.00  per  cent  or  a  little  under.  The  silicon  is  likely  to  av- 
erage around  0.70  per  cent  and  in  malleable  scrap  consist- 
ing of  castings  worn  out  in  service  the  sulphur  is  from  0.06 
to  0.10,  the  manganese  0.25  to  0.35  and  the  phosphorus  from 
0.16  to  0.20  per  cent.  In  the  case  of  agricultural  and  other 
light  work,  the  initial  carbon  may  have  been  considerably 
higher,  but  in  view  of  the  lightness  of  cross  section  this  ele- 
ment may  have  been  much  reduced,  possibly  to  1  per  cent 
and  under.  The  silicon  generally  is  somewhat  higher  than 
in  the  heavier  materials,  usually  averaging  about  85  per 
cent.  The  other  elements  are  about  as  in  railway  malleable. 

Malleable  scrap  is  open  to  the  objection  that  when  used 
as  a  considerable  percentage  of  the  mix  in  air  furnace  or 
open-hearth  practice,  serious  errors  may  be  introduced  in  the 
chemical  composition  of  the  charge.  This  condition  is  ag- 
gravated if  the  malleable  scrap  includes  gray  iron  scrap  rich 
in  carbon,  silicon  and  phosphorus.  It  is  a  most  reprehen- 
sible practice  of  a  number  of  junk  dealers  either  to  purposely 
mix  or  to  not  properly  separate  the  two  materials,  thus 
practically  destroying  the  value  of  the  malleable  scrap  to 
the  malleable  founder.  This  separation  can  be  readily  made 
only  'at  the  point  of  origin  as  the  user  has  no  commercially 
effective  method  of  inspection.  Equally  harmful  in  the  op- 
posite direction  is  the  admixture  'of  steel. 

Another  source  of  -trouble  is  the  introduction  of  un- 
known amounts  of  rust  into  the  charge  when  melting  scrap 
that  has  been  exposed  to  weather.  Some  scrap  may  con- 
tain 5  per  cent  or  more  of  rust  which  of  course  is  a  dead  loss 
in  melting.  It  also  forms  a  highly  oxidizing  slag  which  in 
turn  strongly  acts  on  the  silicon  and  carbon  causing  unpre- 
dictable changes  of  composition  in  melting.  The -effects  of 
this  evil  can  be  minimized  by  the  use  of  clean  scrap,  which 
unfortunately  cannot  be  purchased  and  by  the  purchase  of 

94  American  Malleable   Cast   Iron 

scrap  of  such  form  that  it  presents  little  surface  to  rusting. 

For  this  reason  and  because  of  the  high  labor  cost  of 
handling  small  scrap,  agricultural  material  is  not  a  satis- 
factory melting  stock  in  air  furnace  or  open-hearth  mal- 
leable practice.  Heavy  malleable  scrap  stored  out  doors 
but  not  extremely  heavily  rusted  usually  behaves  as  though 
it  contained  about  1.75  per  cent  carbon  and  0.47  per  cent 
silicon.  The  presence  of  adulterations,  except  of  high  phos- 
phorus material,  is  of  less  consequence  in  electric  furnace 
melting  than  with  air  furnaces  or  open  'hearths.  Malleable 
scrap  is  used  not  because  it  is  a  means  of  cheapening  the 
metal  but  for  the  definite  purpose  of  regulating  the  carbon 
content  of  the  mix.  Successful  air  furnace  practice  requires 
a  c'harge  averaging  around  3  per  cent  in  carbon,  hence  some 
low  carbon  stock  must  be  used  to  mix  with  pig  iron  which 
is  always  of  much  'higher  percentage  of  carbon  content. 

Sprue  is  available  in  a  quantity  dependent  on  the  found- 
ry practice  but  not  usually  sufficient  to  bring  down  the  car- 
bon as  far  as  necessary.  Hence  recourse  is  had  to  mal- 
leable or  steel  scrap.  The  use  of  scrap  for  the  purpose  of 
making  up  different  'amounts  of  sprue  has  been  practiced  for 
more  than  30  years.  The  Chicago  Malleable  Iron  Works 
has  purchased  scrap  for  air  furnace  charges  on  a  commer- 
cial scale  since  1885  and  in  1888  the  practice  was  well  es- 
tablis'hed.  Possibly  others  adopted  it  still  earlier. 

Steel  scrap  is  an  article  of  commerce.  What  has  been 
said  of  -malleable  regarding  freedom  from  rust  and  from  ad- 
mixture of  other  forms  of  scrap  applies  equally  well  to  steel. 
In  addition  there  is  a  certain  danger  from  the  possible  pres- 
ence of  alloy  steels  which  may  introduce  entirely  unexpected 
elements.  A  case  in  point  is  the  high  manganese  steel  used 
in  frogs,  switch  points  and  cross  overs  and  containing  up  to 
about  13  per  cent  manganese. 

The  carbon  content  of  all  steels  is  relatively  low,  rang- 
ing from  around  0.90  to  1.00  per  cent  in  some  spring  steels 
down  to  0.25  or  0.30  per  cent  in  castings.  The  silicon  is 
always  low  and  the  manganese  averages  around  0.50  or  0.60 

Melting  Stock  95 

per  cent.  The  sulphur  and  phosphorus  values  are  always 
lower  than  in  any  other  ingredient  in  the  charge.  Consid- 
ering the  fact  that  the  material  is  always  somewhat  rusty  it 
may  be  classed  as  pure  iron  in  calculating  a  mix. 

Heavy  steel  scrap  is  preferable  to  the  lighter  material 
as  is  the  case  with  malleable  scrap.  Thin  sheet,  small  clip- 
pings, rods,  pipe  and  light  structural  material  are  particu- 
larly objectionable  when  rusty  or  burned. 

Steel,  as  in  the  case  of  malleable  scrap,  is  used  to  reduce 
the  carbon  content  of  the  mix.  Being  lower  in  carbon  a 
less  percentage  suffices  for  a  given  purpose ;  therefore  there 
is  less  danger  of  introducing  large  errors  of  calculation  in  , 
computing  the  mix  or  of  large  amounts  of  rust  to  compli- 
cate the  reactions. 

Steel  is  rarely  used  in  making  cupola  or  electric  furnace 
malleable.  Its  general  use  was  adopted  more  recently  than 
that  of  malleable  scrap,  but  the  old  records  of  the  Indian- 
apolis plant  of  the  National  Malleable  Castings  Co.  show  that  for 
an  extensive  period,  beginning  in  August,  1887,  steel  was 
regularly  vised  in  the  mix,  and  that  the  practice  continued 
as  circumstances  warranted.  The  author  has  no  facts  to  in- 
dicate whether  this  practice  was  original  with  the  late 
James  Goodlet,  then  in  charge  thei;e,  or  copied  from  some 
other  plant. 

Wrought  iron,  which  chemically  is  merely  an  extremely 
low  carbon  steel,  was  used  at  the  inception  of  the  industry, 
Boyden  referring  to  it  in  his  notes.  At  a  later  date  it  was 
regarded  as  harmful  arid  at  present  it  is  not  available  in 
sufficient  quantity  to  possess  interest. 

Pig  iron  is  the  raw  material  which  makes  up  the  bulk 
of  the  tonnage  from  which  malleable  cast  iron  is  made.  In 
the  days  of  the  fathers  of  the  industry  charcoal  iron  was 
generally  if  not  universally  used.  Then,  as  now,  it  was 
made  from  relatively  low  phosphorus  ores.  In  the  early 
days,  before  the  Civil  war,  the  references  are  mostly  to 
irons  smelted  in  New  Jersey  arid  Connecticut  from  eastern 
ores  using  charcoal  from  local  forests.  Bovden  used  such 


American   Malleable    Cast   Iron 

Melting  Stock  97 

irons.  Alfred  Hammer  used  New  Jersey  coke  arid  anthra- 
cite pig  as  early  as  1878.  In  about  1885  there  was  'a  no- 
ticeable trend  toward  the  use  of  coke-melted  pig  iron,  first, 
as  far  as  the  author  can  judge,  in  the  case  of  very  soft  pig 
iron.  This  was  high  in  silicon,  and  was  unusual  in  furnaces 
operating  as  cold  as  did  the  usual  cold  blast  charcoal  fur- 
naces of  the  period. 

The  impression  is  quite  general  among  the  older  found- 
rymen  that,  apart  from  differences  of  composition,  there 
are  differences  in  properties  as  between  the  products  of 
different  furnaces.  Many  also  believe  that  it  is  preferable 
to  use  iron  from  several  producers  in  each  heat.  It  is  not 
clear  to  the  author  upon  what  metallurgical  considerations 
such  differences  could  be  based.  Undoubtedly  before  the 
days  of  analyzed  pig  iron,  these  beliefs  were  based  on  sound 
reason;  at  present  they  would  seem  to  be  little  more  than 
prejudice  as  applying  to  malleable  practice. 

A  similar  situation  is  encountered  in  a  somewhat  gen- 
eral feeling  that  the  use  of  malleable  scrap  is  in  some  way 
connected  with  the  substitution  of  coke  for  charcoal  pig. 
It  has  been  only  relatively  recently  that  interest  in  the 
control  of  the  product  by  limiting  the  total  carbon  content 
became  at  all  general.  Dr.  Moldenke  in  his  book,  "The 
Production  of  Malleable  Castings"  (1911),  recommends  for 
instance  that  the  carbon  be  not  below  2.75  per  cent  and 
may  range  up  to  3  per  cent.  Presumably  this  represents 
the  best  general  understanding  of  the  time.  While  since  1906 
certain  manufacturers  realized  the  relation  between  carbon 
and  strength  and  acted  on  this  knowledge,  it  is  not  sur- 
prising that  in  the  days  when  the  substitution  of  coke  for 
charcoal  iron  began  the  mixes  used  never  were  based  on 
considerations  of  carbon  content. 

With  low  silicon  charcoal  iron  available  it  was  easy  to 
secure  silicons  low  enough  to  produce  a  white  fracture  by 
the  use  of  pig  and  sprue  alone.  Hot  blast  coke  irons  always 
contained  enough  silicon  so  that  some  material  other  than 
the  available  amount  of  sprue  was  required  to  reduce  the 


American   Malleable    Cast   Iron 



Melting  Stock  .  99 

silicon  content  sufficiently  to  avoid  "mottled"  castings.  The 
effect  of  this  change  of  practice  on  carbon  content  was  totally 
disregarded  except  by  a  very  few  observers. 

The  general  observation  that  charcoal  iron  malleable 
could  and  should  be  made  lower  in  silicon  than  malleable 
for  the  same  purpose  made  from  coke  iron  probably  was 
true.  However,  it  originated  merely  from  the  reduction  in 
carbon  which  unconsciously  accompanied  the  changed  prac- 
tice and  not  from  the  method  of  making  the  pig. 

Where  malleable  was  made  from  charcoal  .and  coke 
iron  of  the  same  silicon  content  the  former  was  somewhat  the 
stronger,  due  to  its  somewhat  lower  carbon  content,  which 
in  turn  was  due  to  lower  furnace  temperature. 

In  view  of  such  former  experiences  great  caution  should 
be  used  in  regarding  as  cause  and  effect  phenomena  without 
apparent  logical  connection. 

The  transition  from  charcoal  to  coke  iron  has  extended 
over  many  years  and  is  not  yet  complete.  In  the  early 
ninety's  coke  iron  was  used  very  sparingly,  but  10  years 
later  the  coke  iron  was  far  in  the  ascendant.  At  present 
comparatively  few  manufacturers  continue  the  use  of  char- 
coal pig  and  they  employ  it  only  in  limited  quantity. 

To  the  writer  it  has  seemed  that  this  retention  of  char- 
coal iron  results  either  from  sentiment  pure  and  simple  or 
from  a  superstitious  belief  that  for  some  unexplained  rea- 
son a  modicum  of  charcoal  pig  imparts  a  mysterious  virtue 
of  unknown  character  to  the  resulting  product.  Being 
smelted  at  a  lower  temperature,  charcoal  iron  differs  from 
coke  iron  in  being  generally  lower  in  carbon.  On  account 
of  the  low  sulphur  fuel,  it  is  always  lower  in  sulphur.  Also 
the  range  of  silicon  values  commonly  available  run  lower  in 
charcoal  than  in  coke  iron.  Again,  this  is  the  result  of  the 
furnace  temperature. 

The  lowest  silicon  charcoal  pig  irons  commercially 
made  contain  less  silicon  than  the  lowest  silicon  grades  of 
coke  iron.  Moreover,  high  silicon  coke  iron  is  more  com- 
monly obtainable  than  charcoal  iron  with  the  same  con- 


American  Malleable    Cast   Iron 



Melting'  S-otk  :  101 

tent,  in  spite  of  the  fact  that  the  "Scotch"  grades  of  charcoal 
pig  have  a  high  silicon  content. 

The  writer  has  never  been  able  to  see  any  theoretical 
reason  why  charcoal  iron  should  make  a  better  product  than 
coke  iron,  given  a  correct  final  composition.  The  late  J.  B. 
Johnson  Jr.,  who  dealt  at  length  with  the  subject  from  the 
blast  furnace  viewpoint,  ascribed  the  differences  to  the  in- 
direct effect  of  oxygen.  For  the  best  available  opinions  in 
this  subject,  the  interested  reader  is  referred  to  the  pub- 
lished reports  on  Johnson's  pioneer  wrork  on  this  subject  in 
the  Transactions  of  the  American  Institute  of  Mining  and 
Metallurgical  Engineers.  In  view  of  the  radical  alterations 
made  in  the  raw  material  during  the  malleable  process  it  is 
difficult  to  see  how  any  differences,  such  as  the  form  of 
crystallization  of  graphite  in  the  pig  iron,  could  survive  the 
chemical  and  physical  changes  involved.  The  trade  as  a 
whole  seems  to  look  upon  the  matter  in  this  light  and  from 
a  tonnage  viewpoint,  charcoal  iron  is  of  little  importance  in  the 
malleable  industry. 

The  production  of  malleable  cast  iron  requires  the  use 
of  relatively  low  phosphorus  ores,  those  of  the  Lake  Superior 
region  being  the  most  available  for  the  purpose.  Conse- 
quently, many  of  the  blast  furnaces  producing  malleable  pig 
are  situated  along  the  lake  ports.  The  proximity  to  the 
Pennsylvania  coal  fields  producing  coking  coals,  has  formed 
another  area  extending  from  Pittsburgh  down  the  Ohio  river 
and  up  the  Mahoning  and  Shenango  valleys.  The  charcoal 
furnaces  are  located  near  the  ore  fields  in  heavily  wooded 
districts.  The  ore  fields  of  Minnesota,  Wisconsin  and  north- 
ern Michigan  are  shown  in  the  form  of  a  shaded  area  in 
Fig.  47.  Immediately  adjacent  to  this  section  are  the  prin- 
cipal charcoal  furnace  plants,  shown  on  the  map  by  open 
circles.  The  coke  furnace  plants  are  shown  as  solid  circles. 
Most  blast  furnaces  do  not  make  pig  iron  for  one  purpose 
only,  but  the  map  is  intended  to  include  all  important  pro- 
ducers of  this  class  of  metal  in  considerable  quantities.  An 
open  pit  mine  on  the  Mesabi  range  "is  shown  in  Fig.  48. 


Matictiblc    Cast   Iron 

Melting  Stock  103 

The  ores  from  which  malleable  pig  iron   is   made  'have  ap- 
proximately   the   following   composition  : 

Per  cent 

Fe   51.5,   present   as    Fe3O3 . . 75.57 

P   .086,   present   as    P2O5 19 

Mn.    .40   to    .70,   present   as    MnO ' 77* 

Si02      9.50 

A1203 2.75 

CaO     70 

MgO    bO 

H2O,    CO2  and   undetermined    10.02 


Malleable  pig  iron  is  sold  with  ti  guaranteed  maximum 
of  0.05  per  cent  in  sulphur,  usually  of  either  0!19  or  0.20 
per  cent  in  phosphorus  and  is  furnished  with  from  about 
1.00  to  2.00  per  cent  silicon,  although  'higher  values  are 
sometimes  required.  The  manganese  varies  from  about  0.50 
to  .about  0.90  per  cent,  the  lower  and  higher  values  being 
encountered  frequently.  The  average  carbon  content  for  the 
country  is  now  and  lias  been  for  at  least  15  years  close  to 
4.10  per  cent,  individual  lots  running  normally  from  3.85  to 
4.40  per  cent,  'i  he  carbon  content  practically  is  fixed  by  the 
blast  furnace  temperature. 

Pig  iron  may  be  either  sand,  chill  or  machine  cast.  The 
former1  carries  with  it  a  certain  amount  of  sand  fused  into 
the  surface.  The  chill  and  machine  cast  irons  are  free  from 
this  foreign  matter,  which  fact  presents  a  certain  advantage 
both  because  nothing  but  iron  is  paid  for  and  because  less 
dirt  is  carried  into  the  furnaces.  The  two  latter  classes, 
being  rapidly  cooled,  contain  more  combined  and  less  free 
carbon  than  the  former,  other  things  being  equal.  The 
melting  point  and,  presumably,  the  latent  heat  of  fusion  are 
thereby  decreased.  It  is  claimed  that  a  material  fuel  econ- 
omy results.  On  all  accounts  the  use  of  machine  cast  iron 
can  present  no  disadvantages  to  compensate  for  the  advan- 
tages outlined  above  and  its  greater  uniformity  of  size  and 

Recently  there  his  been  a  decided  tendency  toward 
changes  in  chemical  composition  of  commercial  pig  iron. 
Up  to  1914  the  sulphur  content,  while  guaranteed  as  0.05, 
was  nearly  invariably  under  0.03  in  the  Ohio  and  Illinois 


American   Malleable    Cast   Iron 

Melting  Stock  105 

irons.  Since  then  fuel  conditions  have  so  far  deteriorated 
the  quality  of  coke  available  that  at  present  sulphur  is  usually 
only  a  little  under  0.05  per  cent  and  occasionally  exceeds 
that  figure.  Ten  or  15  years  ago  iron  often  was  sold  with 
a  maximum  phosphorus  of  0.16  per  cent,  no  extra  price  be- 
ing charged  as  compared  with  a  0.19  or  0.20  per  cent  maxi- 
mum specification.  The  gradual  increase  in  the  ratio  of 
phosphorus  to  iron  in  the  product  of  the  Mesabi  ore  fields 
has,  however,  forced  an  increase  to  the  latter  figures  as  a 
phosphorus  maximum. 

For  about  five  or  six  years  there  has  been  a  decided 
trend  toward  lower  carbon  malleable,  brought  about  by  the 
demand  for  increased  quality  of  product.  This  results  in 
lower  percentages  of  pig  iron  in  the  mixes  than  formerly 
and  therefore  requires  increasingly  a  higher  silicon  content 
to  maintain  the  former  silicon  values  in  the  product  and  in 
some  cases  raise  them  -slightly.  Accordingly  the  metal  con- 
taining under  1.25  per  cent  silicon  is  now  almost  useless 
and  most  -plants  require  some  pig  iron  up  to  2  per  cent  and 
possibly  over  in  silicon.  The  average  silicon  content  in  all 
the  pig  iron  consumed  in  the  malleable  industry  is  doubtless 
between  1.60  and  1.70  per  cent. 

There  seems  to  be  increasing  difficulty  in  getting  any 
low  manganese  pig.  However,  this  stringency  has  been 
somewhat  counteracted  by  the  decreased  amount  of  pig  re- 
quired and  the  increased  sulphur  content.  Coke  pig  iron 
under  1  per  cent  in  silicon  and  usually  high  in  sulphur,  is 
generally  the  product  of  an  abnormal  furnace  condition,  re- 
sulting in  cold  working  and  is  not  of  a  composition  suitable 
to  modern  requirements. 

High,  silicon  pig,  or  blast  furnace  ferrosilicon  is  a  metal 
usually  running  about  10  per  cent  in  silicon.  Its  principal 
source  is  Jackson,  O.  The  phosphorus,  sulphur  and  carbon 
are  kept  low.  The  metal  is  used  as  a  source  of  silicon  when 
suitable  pig  is  not  available.  In  the  electric  furnace  process, 
it  may  furnish  most  of  the  silicon  of  the  cupola  charge. 

Ferromanganese  is  a  blast  furnace  product  made  from 
manganese  ores.  It  usually  contains  from  70  to  85  man- 
ganese and  nearly  6  per  cent  carbon.  Silicon,  sulphur  and 


American  Malleable   Cast   Iron 


Melting  Stock  107 

phosphorus  are  low,  iron  being  the  principal  element,  other 
than  manganese  and  carbon.  Ferromanganese  is  used  gen- 
erally in  -the  form  of  an  addition  to  the  molten  metal  to 
supply  a  deficiency  in  manganese. 

Electric  furnace  ferrosilicon  contains  nominally  15,  50, 
75  and  95  per  cent  silicon.  The  50  per  cent  alloy,  actually 
running  from  48  to  54  per  cent  silicon,  is  most  commonly 
used.  In  addition  to  silicon  and  iron  the  metal  contains 
phosphorus,  sulphur,  aluminum  and  calcium.  These  elements 
are  not  usually  present  in  important  amounts. 

Ferrosilicon,  being  readily  oxidized,  is  not  suitable  for 
cupola  use.  When  charged  into  an  air  furnace  with  the 
melting  stock  it  must  be  protected  from  contact  with  fur- 
nace gases  as  far  as  possible.  It  is  generally  used  as  addi- 
tions to  the  molten  heat. 



THUS    far  we  have  dealt  with  the  raw   material   actually 
entering    the    product.      There    remain    two    other    classes 
of   raw  materials   which,  although  they   form  no   part  of 
the  finished  product,  are  used  in  such  quantities  and  so  affect 
the  shop  operation  as   to   be  of   decided   industrial   importance. 
The  first  of  these  groups  is  fuel. 

The  fuels  used  in  the  malleable  industry  may  be  classi- 
fied as  melting  fuel,  annealing  fuel  and  power  plant  fuel. 
The  latter,  although  it  may  be  used  in  large  quantites,  as 
in  electric  furnace  plants,  should  be  considered  from  the 
viewpoint  of  power  plant  practice  rather  than  from  a 
metallurgical  angle.  Melting  fuels  not  only  furnish  heat  but 
also  very  distinctly  affect  the  composition  of  the  resulting 
product.  On  the  other  hand,  annealing  fuels  need  be  consid- 
ered only  from  the  standpoint  of  combustion. 

The  original  source  of  almost  all  the  heat  used  in  melting 
and  annealing  malleable  is  coal,  although  it  may  be  convert- 
ed before  use  into  coke,  illuminating  gas,  water  gas,  or 
producers  gas.  Oil  and  natural  gas  are  also  industrially  im- 
portant in  some  localities  and  for  some  purposes. 

Bituminous  coal  is  very  widely  distributed  throughout 
the  country,  as  indicated  in  Fig.  53.  Anthracite  and  lignite 
are  not  important  metallurgical  fuels  and  are  therefore  omit- 
ted from  the  map.  Anthracite  was  formerly  used  as  a  cupola 
fuel  and  at  an  early  date,  possibly  1838  was  used  for  anneal- 
ing by  Belcher.  It  is  still  used  in  at  least  one  plant  for 
this  purpose. 

Coal  from  practically  any  of  the  bituminous  fields  shown 
may  be  used  for  annealing,  the  choice  generally  being  based 
on  geographic  and  commercial  considerations  rather  than 
on  the  properties  of  the  fuel  from  any  given  field.  Mine  run 
fuel  is  generally  used  in  annealing  for  hand  firing.  The  crite- 
rion of  quality  is  the  absence  of  ash  and  water,  these  fac- 


American   Malleable   Cast  Iron 








Fuel    and    Refractories  111 

tors  representing  increased  cost  and  operating  trouble  and 
not  metallurgical  suitability.  -A  low  ash  fuel  is  sometimes 
preferred  for  use  with  pulverized  fuel  annealing  equipment 
in  order  to  avoid  trouble  from  the  ash  settling  in  the  fur- 
naces and  flues.  The  requirements  of  a  crushing  plant  prac- 
tically necessitate  a  fuel  either  quite  dry  as  received  or 
dried  artificially  before  crushing. 

-  Since  lump  coal  is  of  no  advantage,  pulverized  fuel 
plants  buy  the  smaller  commercial  sizes  of  fuels.  However, 
the  selection  of  fuel  for  crushing  in  annealing  practice  is  not 
well  standardized.  The  author  knows  of  two  large  and  ably 
managed  plants  within  a  few  miles  of  each  other,  both  an- 
nealing with  pulverized  fuel.  One  buys  a  high  ash  local  coal 
and  removes  about  10  to  12  per  cent  of  water  by  drying  be- 
fore crushing,  while  the  other  obtains  coal  in  the  eastern 
fields  hundred  of  miles  distant  which  runs  under  2  per  cent 
in  water. and  around  3  to  4  per  cent  in  ash.  The  subject 
of  coal  for  'annealing  is  therefore  easily  dismissed  with  the 
statement  that  practically  any  local  fuel  can  be  employed, 
economical  conditions  alone  governing  the  selection. 

In  the  case  of  the  melting  coals  conditions  are  quite 
different.  Here,  in  addition  to  the  purely  economic  prob- 
lems, there  enter  many  other  considerations  which  narrow 
down  the  choice.  Coal  burned  in  the  air  furnace  is  expected 
to  furnish  heat  units  as  economically  as  may  be  practicable, 
and  must  have  certain  other  definite  characteristics.  It  must 
burn  with  a  long  luminous  flame  jof  sufficient  volume  to  en- 
tirely fill  the  air  furnace.  It  must  be  so  low  in  sulp'hur  as  not 
to  prohibitively  raise  the  content  of- that  element  in  the  met- 

Its  character  must  be  such  that  none  of  the  constituents 
will  melt  and  run  to  a  tarry  mass  at  the  temperature  of  the 
fire.  Its  ash  must  be  fairly  low  in  amount  and  of  such  char- 
acter as  not  to  fuse  together  into  clinker's  at  fire  ibox  tem- 
peratures. Its  moisture  content  must  -be  reasonably  low  in 
order  to  maintain  good  flame  conditions. 

These  characteristics  are  found  in  coal  from  a  very  limit- 
ed geographical  area  which  is  shown  in  black  in  Fig.  53. 


American   Malleable   Cast   Iron 


'Fuel    and    Refractories  113 

In  the  writer's  experience  the  fuel  varies  even  within  this 
district,  'being  in  general  better  in  the  southern  portion  of  the 

No  entirely  satisfactory  method  of  judging  the  quantity 
of  a  melting  coal,  except  by  actual  test  is  available.  This 
arises,  in  part,  from  the  fact  that  the  behavior  of  the  fuel  is 
dependent  on  the  actual  combustion  conditions  encountered 
which  differ  with  different  furnaces.  The  composition  of  a 
few  good  melting  fuels  is  shown  in  Table  II. 

Table  II 








Vol.  Comb.    . 





Fixed   carbon    .  .  . 

,  .  .  .       58.32 




B.t.u.   per  pound....       13,902  13,434  14,058  14,276 

There  is  a  general  preference  for  coal  under  1  per  cent 
sulphur,  although  the  sulphur  which  the  melt  takes  up  de- 
pends not  only  on  the  •sulphur  content  of  the  fuel  but  also 
on  the  form  in  which  it  is  present.  Some  fuels,  moderately  high 
in  sulphur,  produce  metal  lower  in  sulphur  than  other  fuels, 
much  lower  in  that  element.  Many  coals  exist,  even  some  in  the 
Illinois,  Indiana  and  central  Kentucky  fields  which  based  on 
composition  should  work  admirably.  The  expectation,  however, 
is  not  borne  out  in  practice. 

What  makes  a  long  flame  coal  has  never  been  definitely 
determined.  The  flaming  coals  are  in  general  the  coals  best 
adapted  to  making  illuminating  gas.  The  flaming  quality 
is  associated  with  the  distillation  products  of  the  fuel  when 
heated  in  the  fire  box.  The  running  of  the  coal  is  a  phenome- 
non of  the  same  character.  The  low  moisture  seems  to  be 
a  necessary  characteristic.  Goals  of  this  character  artificial- 
ly wetted  behave  differently  from  the  naturally  wetter  In- 
diana-Illinois fuels. 

The  clinkering  of  the  ash  is  largely  a  matter  of  chemical 
composition.  Strictly  speaking  it  depends  on  the  com- 


American   Malleable   Cast  Iron 

Fig.  55 — Picking  table  in  a  coal  tipple,  showing  facilities  for  removing 
slate,  sulphur,   etc.,  by  hand. 

Fig.    56 — Adjustable   loading   boom   which   places    coal    in   car    without 


Fuel   and    Refractories  115 

pounds  formed  in  the  ash  under  the  temperature  and  chem- 
ical conditions  existing  in  the  fuel  bed.  Therefore,  analyses 
made  on  laboratory  preparations  of  as-h  are  not  correct  state- 
ments of  what  may  happen  in  the  fuel  bed,  but  are  of  some 
value  as  indicating  what  may  be  expected.  An  ash  of  a 
very  satisfactory  fuel  had  the  following  composition : 


Per   Cent 
44  52 


43  75 


1  32 


5  72 


.  .  .      .                                1  05 




.  (  3.64 

The  analysis  is  of  a  laboratory  preparation  of  the  ash. 
On  the  grates  the  Fe,O3  would  be  largely  reduced  to  FeO. 

The  fusing  point  of  the  ash  of  eastern  coals  is  2400  to 
2850  degrees  Fahr.  Above  2600  degrees  Fahr.  is  preferable. 

In  general,  the  absence  of  iron  oxide,  alkalies  and  lime 
in  the  order  given  is  considered  a  desideratum. 

The  ash  and  sulphur  contents  of  coal  are  considerably 
affected  by  the  method  of  preparation  and  in  recent  years 
mining  conditions  have  been  such  as  to  make  for  a  steady 
deterioration  along  these  lines. 

Air  furnaces  require  a  lump  coal  for  their  fuel  'but  com- 
mercial practice  varies  as  to  the  size  of  screen  over  which 
the  coal  should  be  passed  before  shipment.  Some  foundry- 
men  desire  coal  not  finer  than  that  which  will  not  pass  a 
4-inch  mesh,  while  others  tolerate  all  that  will  pass  over  a 
^4-inch  screen.  The  beslt  practice  probably  is  a  little  nearer 
the  latter  figure  than  the  former — say  about  1^2-inch  screened 

When  fuel  is  to  be  burned  in  pulverized  form  in  melt- 
ing furnaces  the  quality  of  coal  required  is  the  sam'e  as  for 
direct  combustion  on  the  grates,  except  that  the  smaller 
sizes  of  coal  can  be  utilized. 

A  number  of  engineering  concerns  have  developed 
highly  specialized  plants  for  grinding  and  pulverizing  coal. 
The  sequence  of  operations  in  all  of  them  is  substantially  the 


American    Malleable   Cast  Iron 







Fuel   and    Refractories  117 

same.  The  coal,  crus'hed  to  fairly  small  size  or  purchased 
after  screening,  passes  through  a  device  where  it  is  dried  by 
a  current  of  warm  air.  A  favorite  method  is  to  feed  it  in  at 
one  end  of  a  rather  long  narrow  cylinder  rotating  on  its 
axis,  whic'h  is  slightly  inclined  to  the  horizontal.  As  the 
cylinder  revolves  the  coal  rolls  over  and  over  and  travels 
toward  and  finally  out  of  the  lower  end  of  the  cylinder.  A 
current  of  warm  air  passes  through  the  cylinder,  usually  in 
the  direction  opposite  the  flow  of  coal. 

From  the  end  of  the  dryer  the  coal  is  automatically  de- 
livered to  a  grinder,  one  type  of  Whic'h  consists  of  an  ar- 
rangement like  the  "fly  balP'  or  centrifugal  governor  of  a 
steam  engine.  The  weights  are  in  the  form  of  rollers  whic'h 
run  against  a  surrounding  ring  when  the  mechanism  is  ro- 
tated. The  fuel  is  ground  to  flour  between  these  rollers  'and 
the  ring,  but  if  any  hard  lump  such  as  a  piece  of  scrap  iron 
should  fail  to  have  been  removed  it  merely  crowds  through 
between  the  roller  and  track  and  does  no  damage. 

Means  are  usually  provided  for  screening  or  otherwise 
separating  insufficiently  ground  material  and  returning  it  to 
be  reground.-  The  product  should  be  reground  to  pass  a  100- 
mesh  sieve  and  75  per  cent  to  pass  a  200-mesh  sieve^  When 
ground  to  size  it  is  transported  by  belt  or  screw r<5onveyor 
to  bins.  A  pulverizing  plant  is  shown  in  Fig.  92. 

In  -general  it  is  well  to  store  only  limited  qu#fitities  of 
ground  coal- -'owing  to  the  fire  hazards.  Dried  pulverized  coal 
absorbs  moisture  readily,  and  sticks  together  and^feeds  to 
the  'burner  in  a  lump  condition  if  it  has  an  opportunity  to 
take  up  water  before  being  used. 

The  transportation  of  coal  dust  by  carrying  it  in  a  cur- 
rent of  air  is  dangero;us,  the  mixture  being  highly  explosive. 
In  the  best  installations  the  air  and  coal  are  mixed  just  as 
near  the  point  of  fen  fry- into  the  furnace  as  possible  to  min- 
imize the  danger. 

Gas  as  a  fuel  is  only  an  indirect  application  of  the  com- 
bustion of  coal,  indeed  it  might  well  be  maintained  that  any 
use  of  coal  for  this  purpose  involves  its  gasification  even 
though  that  process  may  be  carried  out  in  the  fire  box  in- 
stead of  in  a  separate  apparatus. 


American  Malleable  Cast  Iron 



Fuel    and    Refractories 119 

Gas  fuels  are  classified  as  illuminating  gas  or  producer 
gas.  The  former  is  either  a  distillation  product  of  coal,  or  a 
mixture  of  hydrogen,  carbon  monoxide  and  hydrocarbons, 
called  water  gas  and  made  by  the  action  of  steam  on  red 
hot  coke.  Producer  gas  is  a  mixture  of  carbon  monoxide 
and  hydrogen. 

Illuminating  gas  is  too  costly  for  extensive  metallurgical 
operations.  Its  use  is  limited  to  crucible  furnaces  for  brass 
melting,  etc.,  and  small  core  ovens.  If  the  gas  is  a  by-prod- 
uct in  the  manufacture  of  coke,  it  is  commercially  available 
and  then  only  in  the  plant  operating  the  coke  ovens  or  in 
neighboring  plants.  If  the  gas  is  to  'be  piped  any  distance  it 
can  generally  be  more  profitably  sold  for  public  consump- 
tion for  domestic  requirements. 

The  operation  of  a  gas  producer  is  simple  in  principle. 
A  gas  producer  is  merely  a  firebox  in  which  a  deep  bed  of 
fuel  is  burned  with  a  limited  supply  of  air,  the  intention 
being  to  burn  the  carbon  of  the  fuel  to  carbon  monoxide. 

Theoretically,  the  producer  gas  is  air  in  which  the  oxy- 
gen has  been  converted  to  carbon  monoxide  and  should  con- 
tain about  one-third  carbon  monoxide  and  two-thirds  nitro- 
gen. In  practice  the  water  from  the  combustion  of  the  hy- 
drogen of  the  fuel,  the  moisture  of  the  fuel  itself  and  the 
steam  which  is  introduced  with  the  air  supply  to  avoid 
clinkering  all  react  with  carbom,  liberating  some  hydrogen. 
Also  the  fuels  rich  in  volatile  matter  distill  off  more  or 
less  hydrocarbon  gases.  Furthermore,  if  the  fuel  bed  is 
allowed  to  get  uneven  permitting  air  to  come  through,  some 
of  the  carbon  monoxide  is  burned  to  dioxide.  The  latter 
constituent  is  more  prevalent  in  producers  blown  with  steam 
than  in  those  blown  with  air  alone. 

As  a  general  statement  of  the  composition  of  commer- 
cial producer  gas,  the  following  figures  are  quoted  from  Wyer: 

Table    III 


H       CH4     C2H4     N  CO  O       C6a 

Gas  from  hard  coal 20.0        ..         ..  49.5  25.0  0.5       5.0 

Gas    from    soft    coal 10.0      3.0       0.5  58.0  23.0  0.5       5.0 

Gas  from  coke   10.0        ..        ..  56.0  29.0  0.5      4.5 

Gas   air  blast    4.43      ..         . .  62.12  33.04  ..       0.41 

Gas  same  as  above  with  air 

and   steam  blast    .        .    14.00  53.3  27.2  5.5 

120 American  Malleable  Cast  Iron 

The  CO2  values  are  rather  high,  an  attempt  usually  be- 
ing made  to  hold  CO2  to  3  per  cent. 

It  is  obvious  that  the  'heat  value  of  the  gas  from  a  pound 
of  coal  cannot  be  greater  than  the  heat  value  of  the  original 

Fig.  59 — Cross  section  of  a  modern  gas  producer 

pound  of  fuel.     The  combustion  of  carbon   to   CO  liberates 

— or  roughly  30  per  cent  of  the  heat  of  combustion  of 

carbon  to  CO2.  This  heat  is  transmitted  to  the  incoming 
fuel  and  to  the  products  of  combustion  as  well  as  to  the 
producer  structure.  It  finally  leaves  the  producer  by  radia- 

Fuel    and    Refractories  121 

tion  from  the  walls  and  also  as  the  sensible  heat  of  the  gas. 
it  therefore  is  of  advantage,  except  in  open  hearth  practice, 
to  make  the  gas  as  near  the  furnace  as  possible  to  avoid  the 
loss  of  'heat  units  by  coo. ing  the  gas  stream  in  passing 
through  long  ducts. 

Where  the  gas  is  to  be  widely  distributed  or  burned  in 
small  accurately  controlled  burners  a  cleaned  gas  from  which 
tar  and  heavy  hydrocarbons  have  been  removed  is  desirable. 

As  stated  before,  gasification  adds  nothing  to  the  heat 
value  of  the  fuel ;  it  may,  however,  result  in  heat  economy 
due  to  the  better  control  and  more  economical  combustion 
conditions  possible  with  gas  fuel  as  compared  with  solid 

Producer  gas  being  a  fuel  of  rather  low  calorific  power 
usually  is  burned  with  hot  air.  The  use  of  cold  air  does 
not  give  sufficiently  hot  flames  for  melting  operations ;  in- 
deed the  temperature  m'ay  not  be  high  enough  to  maintain 
combustion  unless  a  warm  or  hot  air  supply  is  provided  or 
the  gas  itself  be  fairly  hot. 

Producer  gas  usually  is  made  from  bituminous  coal,  al- 
though wood,  peat,  lignite,  coke  and  anthracite  can  be  used. 
The  requirements  for  producer  gas  fuel  in  general  are  simi- 
lar to  those  for  >air  furnace  fuel.  The  coal  should  be  rea- 
sonably low  in  ash  and  the  ash  should  not  clinker.  The 
coal  must  not  soften  or  swell  on  heating  and  preferably 
should  be  low  in  moisture  and  high  in  volatile  matter.  Fur- 
ther, it  should  be  fairly  uniform  in  size  and,  for  melting  op- 
erations, low  in  sulphur.  However,  there  are  many  bitumin- 
ous coals  giving  good  results  in  producers  which  do  not 
•work  satisfactorily  in  the  air  furnace. 

Coke  is  used  as  ;a  metallurgical  fuel  in  the  malleable 
industry  in  cupola  practice  only.  As  everyone  knows,  it  is 
gas  6r  similar  coal  from  which  the  volatile  matter,  includ- 
ing moisture,  has  been  distilled  in  retorts,  beehive  ovens  or 
by-product  ovens.  It  contains  all  the  ash  in  the  coal  from 
which  it  was  made  and  is  therefore  from  50  to  100  per  cent 
higher  in  ash  than  gas  coals.  The  remainder  of  the  coke  is 
practically  pure  carbon.  All  coke  contains  sulphur  and 
there  is  a  general  feeling1  in  favor  Of  foundry  cokes  con- 
taining less  than  1  per  cent  of  this  element.  Sulphur  is 


American   Malleable   Cast   Iron 

Fuel   and   Refractories  123 

taken  up  by  the  metal  more  readily  in  cupola  practice  than 
in  the  air  furnace,  owing  to  the  fact  that  fuel  and  metal 
come  into  actual  contact  with  each  'other.  Moreover  coke 
must  not  be  too  fine  and  must  be  fairly  strong  to  make  a 
suitable  fuel.  The  ash  should  be  as  low  as  practicable  and, 
if  possible,  siliceous  in  character,  since  it  is  easier  to  add 
basic  materials  to  flux  with  the  ash  than  to  add  acid  'materials. 

The  as'h  is  similar  in  composition  to  that  of  coal  and 
corresponds  to  low  grade  fire  clay.  Cupola  fuel  is  not  of 
great  interest  hi  this  discussion,  owing  to  the  general  aban- 
donment of  cupola  malleable.  In  the  case  of  electric  fur- 
nace practice  in  which  cupola  metal  is  the  raw  material  for 
the  electric  furnaces  it  is,  of  course,  an  important  material. 

Oil  is  found  rather  widely  distributed  throughout  the 
country.  Fig.  53  shows  the  oil  areas,  exclusive  of  oil  shales. 
Oil  has  many  advantages  as  a  fuel,  including  cleanliness,  rel- 
ative freedom  from  sulphur,  convenience  of  distribution  and 
accuracy  of  control  of  combustion  conditions. 

Twenty  or  30  years  ago  it  was  customary  to  burn  local 
crude  oils  just  as  they  came  from  the  ground.  The  need  for 
gasoline  and  lubricating  oils  has  caused  the  abandonment  of 
this  practice  and  today  the  fuel  oil  used  consists  of  the 
residue  remaining  after  the  distillation  of  the  commercially 
important  products.  Nearly  all  the  petroleum  products  are 
hydrocarbons  of  the  methane  series  having  the  general 
formula — 

CrH2I1  +  2 

All  have  nearly  the  same  'heat  value  per  pound,  because 
n  being  a  fairly  large  quantity,  the  atomic  ratio  of  carbon  to 
hydrogen  is  in  all  of  them  very  nearly  1  to  2  corresponding 
to  a  ratio  by  weight  of  6  to  1.  The  more  volatile  com- 
pounds such  as  gasoline,  kerosene,  etc.,  are  the  members  of 
low  molecular  weight  in  which  n  is  from  5  up. 

Fuel  oil  has  been  applied  to  'annealing  furnaces  very 
conveniently.  It  is  a  useful  fuel  in  open-hearth  practice  and 
has  been  successfully  used  in  that  connection  in  the  malle- 
able industry.  Under  favorable  circumstances  it  can  some- 
times compete  for  this  purpose  with  producer  gas  -and  pul- 
verized coal.  Furthermore,  it  is  easy  to  arrange  open-hearths 

124 American  Malleable  Cast  -Iron 

to   permit  the  use  of  either  oil  or  gas  or  oil  or  pulverized 
coal,  which  is  a  convenient  arrangement. 

Attempts  have  been  made  to  burn  fuel  oil  in  air  fur- 
naces. No  particular  difficulty  exists  in  actually  doing  the 
melting,  but  generally  the  process  has  not  been  either  eco- 
nomically or  metallurgically  successful.  J.  P.  Pero  reports* 
what  he  regards  as  satisfactory  results  at  an  Illinois  plant, 
but  even  there  it  is  admitted  that  excessive  oxidization  losses 
were  not  overcome  and  'the  fuel  cost  was  high.  A  plant  in 
Michigan  is  said  to  'have  operated  successfully  with  oil  melt- 
ing, even  at  a  high  unit  cost  for  fuel.  The  details  are  not 
available  to  the  writer. 

Natural  gas  is  actually  the  first  member  of  the  petro- 
leum series  methane  CH4,  corresponding  to  n=l.  It  is 
found  associated  with  petroleum.  Its  rapid  exhaustion  by 
wasteful  use  is  one  of  the  scandals  of  our  economic  system. 
It  formerly  was  used  for  annealing. 

There  remain  for  consideration  '-the  raw  materials  which 
are  grouped  under  the  heading  of  refractories.  These  mate- 
rials include  molding  sand,  fire  sand,  fire  clay,  fire  brick  and, 
to  'a  limited  degree  magnesite,  magnesite  'brick,  silica  brick, 
dolomite,  gannister  and  sands'tone. 

Molding  sands  are  somewhat  widely  distributed  in  na- 
ture and -consequently  each  plant  generally  uses  a  local  sand. 
Molding  sands  are  generally  derived  from  granite  which  has 
weathered  and  are  frequently  found  in  glaciated  areas.  Mold- 
ing sands  differ  among  themselves  and  each  purpose  requires 
a  sand  of  specific  characteristics. 

In  the  malleable  foundry  a  sand  is  desired  consisting  of 
well  rounded  quartz  grains,  of  nearly-  uniform  and  fairlv 
small  size,  coated  evenly  with  a  moderate  amount  on\y  of 
fairly  plastic  but  also  reasonably  refractory  clay.  The  actual 
size  of  grain  and  amount  of  clay  desired  will  vary  with  the 
character  of  the  work.  The  heavier  castings  require  coarser 
and  clavier  sands  than  the  lighter. 

The  uniformity  of  grain  size  and  -roundness  of  grain 
are  desired  in  order  to  give  the  greatest  possible  opportun- 
ity for  the  g-as  to  escape  from  the  molds.  If  too  much  clay 

*Vol.   XXVIIT.   p.   316,   Transactions.   American    Fonndrymen's   asso- 

Fuel    and    Refractories 


Fig.   61. — Operations   in   a  molding  sand  pit 

is  present  or  if  the  'Sand  consists  of  grains  differing  largely 
in  size  the  clay  or  small  silica  grains  partly  obstruct  what 
should  be  openings  between  the  grains. 

The  clay  is  needed  'to  hold  the  sand  in  place.  The  silica 
grain  is  very  refractory,  so  that  the  refractoriness  of  the 
sand  depends  upon  the  property  of  the  clay  coating.  If  the 
clay  contains  lime  or  iron  oxide  the  refractoriness  is  much 
decreased.  Most  sands  contain  vestiges  of  feldspar  from 

Fig.    62. — Hauling   sand   from    a   pit 


American   Malleable   Cast  Iron 


Fuel   and    Refractories  127 

the  original  granite  and  these  sands  are  relatively  easily 

The  analysis  and  screen  test  of  sand  does  not  furnish 
a  good  guide  to  its  usefulness,  as  they  are  difficult  to  in- 

The  United  States  bureau  of  standards  and  the  Ameri- 
can Foundrymen's  association  have  gathered  extensive  data 
w'hich  are  available  to  the  interested  reader. 

Tests  for  porosity,  strength  of  bond,  imperviousness  and 
fusibility  are  more  valuable,  but  a  discussion  of  these  proper- 
ties and  their  relationships  would  be  too  technical  to  interest  the 
general  reader  and  in  the  present  state  of  our  knowledge 
would  be  largely  speculative. 

Frequently  sand  free  of  clay  is  wanted  in  coremaking, 
the  binder  furnishing  all  the  cohesion  desired  and  preventing 
cores  growing  too  hard,  due  to  the  burning  of  the  clay.  For 
such  purpose  wind-blown  lake  or  sea  sands,  nearly  pure 
quartz,  are  generally  used. 

Fire  sands  are  very  pure  silica  sands  usually  in  uniform 
rounded  grains.  They  seldom  contain  over  2  per  cent  of  im- 
purities and  are  used  for  the  bottoms  of  acid  open-hearth 
and  air  furnaces.  The  presence  of  a  small  amount  of  basic 
material  is  required  to  cause  the  sand  to  sinter  properly. 

Sandstone  is  a  naturally  compacted  mass  of  silica  sand 
occasionally  used  in  cupola  and  other  furnace  linings.  Gan- 
nister  is  a  siliceous  sedimentary  rock  of  highly  refractory 
character  used  in  furnace  linings  usually  in  crushed  form. 

Fire  clays  are  refractory  silicates  of  aluminum  occurring 
in  nature.  They  contain  as  impurities  oxides  of  iron,  cal- 
cium and  the  alkalies  as  well  as  some  of  the  rarer  metals. 

The  very  pure  and  refractory  flint  clays  possess  little 
plasticity.  Other  varieties  are  more  plastic  and  also  more 
fusible.  Fire  clay  is  seldom  used  alone,  being  mixed  with 
water  and  crushed  fire  brick  or  silica  sand  to  form  a  mate- 
rial for  patching  furnace  walls.  Fig.  63  shows  the  location 
of  the  principal  supplies  of  molding  sand  and  high  grade  fire 
clay  in  the  United  States.  Clay  fire  brick,  made  from  fire 
clay  usually  at  or  near  the  source  of  clay,  consist  merely 
of  mixtures  of  refractory  and  hard  flint  clays,  ground  fire 


American  Malleable   Cast  Iron 

jS^^v     ^jH^S; 


Fuel   and   Refractories  129 

brick,  ground  gannister  and  a  plastic  fire  clay  formed   into 
shapes  and  burned  at  high  temperatures. 

The  manufacture  of  fire  brick  is  one  of  the  most  im- 
portant ceramic  industries  and  cannot  be  more  than  casually 
referred  to  here.  Brick  differs  in  the  material  used,  the 
fineness  or  coarseness  of  grind,  the  density  to  which  the  ma- 
terial is  compressed  and  the  temperature  at  which  it  is 

The  material  used  -largely  determines  the  refractoriness  or 
melting  point.  Fine  grained,  fairly  dense  and  not  too  hard 
brick  possess  great  strength.  Coarse,  open,  lightly  burned 
brick  resists  rapid  changes  of  temperature.  Fine,  dense,  hard 
burned  brick  resist  penetration  of  slags,  hence  every  use  has 
special  requirements.  A  noteworthy  feature  is  that  all  clay 
brick  shrink  when  first  heated. 

Fire    Clay    Refractories    for    Malleable    Iron     Works 

The  chief  deposits  of  high  grade  flint  fire  clays  are  lo- 
cated in  Pennsylvania,  Kentucky  and  Missouri.  These  clays 
are  formed  from  the  weathering  of  feldspar  and  feldspathic 
rocks  which  have  the  formula  K2O,  A12O3  6  SiO2.  Pure 
kaolins  should  be  A12O3  2SiO2,  2H2O,  the  potassium  silicate 
having  been  dissolved.  The  flint  fire  clays  approach  this 
pure  clay  or  kaolin  in  chemical  composition  except  that  they 
contain  some  iron  oxide  'which  gives  the  burnt  product  a 
yellow  tint.  They  are  a  secondary  or  transported  clay  de- 
posited in  still  water  and  are  found  in  the  carboniferous 
areas  or  coal  measures. 

Where  the  coal  is  thick  the  clay  is  generally  thin,  and 
when  the  coal  'thins  out  to  almost  nothing  the  clay  thickens 
up  to  workable  deposits  eight  to  20  feet  in  thickness. 

These  flint  clays  usually  are  mined  in  the  Pennsylvania 
and  Kentucky  districts,  also  occasionally  in  Missouri,  but 
the  Missouri  flint  clays  often  lie  in  pockets.  In  certain  dis- 
tricts, such  as  at  Mexico,  Missouri,  extensive  deposits  are 
worked  'by  stripping  the  overburden  and  then  mining  in  an 
open  pit. 

The  following  chemical  analysis  of  raw  clay  and  burnt 


American   Malleable   Cast  Iron 

Fuel   and   Refractories  131 

bricks  will  illustrate  typical  compositions  for  malleable  fur- 
nace work: 

Table  IV 


Pennsylvania  Missouri  Kentucky 

SiO3     53.05  55.29                       54.41 

A12O3    41.16  40.18  .    36.20 

Fe2O3   2.65  2.44                         2.10 

TiO,     1.80  0.00                         0.00 

CaO    0.00  0.00                         2.13 

MgO    0.00  0.71                         5.16 

Alkalies' 1.34  0.76                         9.39 

Fluxes     5.79  3.91 

Cones      32-33  34                            31 

Ram'  Clay  Analysis  Missouri  Flint  Clays 

Per   Cent 

Loss    on    ignition    12.66 

Si02 49.08 

Al,0,    35.67 

Fe3O3   1.28 

CaO      -. 0.00 

MgO    .:....  0.63 

Alkalies , ., 0.68 

Fluxing  parts    , , -...,.;; 2.59 

Free     silica 7.6 

The  clay  is  ground  and  screened  in  a  dry  pan  in  some' 
plants  while  others  put  the  raw  clay  in  a  wet  pan  and  add 
excess  water  making  the  clay  plastic  and  then  introduce  the 
correct  per  cent  of  coarse  grog,  chamotte  or  calcine.  The] 
latter  is  simply  burnt  clay  crushed  to  coarse  .sizes  •£©  'help 
take  care  of  strains  occurring  in  brick  in  malleable  iron 

The  clays  are  all  pugged  in  a  wet  pan  as  this  process 
develops  the  greatest  placticity.  This  mud  is  carried  to  the 
molder  who  works  up  portions  of  it  into  long  (soft  mud) 
bricks  and  then  throws  them  with  great  force  into  the  molds 
which  are  bumped  several  times  to  cause  the  clay  to  fill  the 
molds  and  give  good  sharp  corners.  These  brick  then  are 
carefully  dried  on  a  steam-heated  floor. 

In  a  num'ber  of  plants  and  for  certain  purposes  brick 
instead  of  being  molded  as  described  are  pressed  hard  be- 
fore drying  giving  increased  density. 

When  thoroughly  dried  the  brick  are  trucked  to  kilns 
where  they  are  set  as  shown,  Fig.  67,  leaving  spaces  for 
heat  and  draft.  The  kilns  are  down  draft,  fired  with  coal, 


American   Malleable   Cast  Iron 

Fuel    and    Refractories  133 

natural  or  producer  gas,  the  gas  being  used   more  on   con- 
tinuous kilns. 

Silica  brick,  used  for  very  high  temperatures,  as  in  the 
roofs  of  open-hearth  and  electric  furnaces,  is  a  brick  made 
like  a  clay  brick  in  which  the  material  is  nearly  all  silica, 
using  only  enough  clay  to  permit  the  brick  to  be  burned  to 
hold  together.  They  are  very  hard,  very  dense,  and  possess 
an  enormous  coefficient  of  thermal  expansion.  They  are 
strong,  almost  infusible,  but  will  not  withstand  sudden  tem- 
perature changes. 

ft  W 

Hi  l|  ! 

::.  ~  -^t,     •S-^W-  »~  W^  W^*:  ju^fr.,     M 

Fig.  67. — Firebrick  and   special    fireclay  shapes   in  a  kiln   ready   to   be 


Magnesia  consisting  of  MgO,  obtained  by  heating  the 
mineral  magnesite,  whic'h  is  MgCOa,  to  expel  the  car'bon 
dioxiide,  is  used  both  ground  and  as  brick  in  basic  furnace 
linings.  •  In  the  malleable  industry  it  is  used  only  in  electric 
furnaces.  It  is  very  refractory  and  resists  basic  slags.  It 
conducts  heat  readily  and  must  be  backed  up  by  a  layer  of 
clay  brick  if  heat  losses  are  to  be  made  a  minimum.  It  has 
relatively  little  strength. 

Dolomite,  a  double  carbonate  of  calcium  and  mag- 
nesium, is  used  in  electric  furnace  bottoms.  It  is  burned 
before  use,  resulting  in  a  mixture  of  CuO-f-MgO  in  the  ratio 
of  about  1.4  to  1.0.  The  commercial  preparations  may  contain 

134  American   Malleable   Cast   Iron 

from  8  per  cent  to  25  per  cent  of  other  oxides,  namely  SiCX, 
A12O3,  and  Fe2O3.  Some  producers  purposely  add  iron  oxides 
(or  silicates)  feeling  that  the  material  then  deteriorates  less  in 
storage  and  sinters  better. 

Chromite,  zirkite,  and  bauxite,  oxides  of  chromium,  of  zir- 
conium, and  of  aluminum  respectively,  possess  no  commercial 
significance  in  the  malleable  industry,  although  they  are  well 
known  refractories.  Carborundum,  silicon  carbide,  is  another 
refractory  which  has  not  found  application. 



THE   air    furnace   is   the    commonest    device   employed   for 
melting    malleable     iron,     having    supplanted    the     cupola 
on    the    score    of    quality    and    the    crucible    furnaces    of 
early  days  on  the  score  of  production  and  economy. 

The  air  furnace  is  of  the  reverberatory  type  in  which 
the  metal,  in  the  form  of  a  fairly  shallow  bath,  is  melted  by 
the  flame  from  fuel  burning  in  a  firebox  at  one  end  of  the 
hearth.  The  flame  is  drawn  over  the  hearth  by  a  stack  at 
the  opposite  end  from  the  firebox.  In  the  earliest  type,  the 
stack  was  at  one  side  with  a  charging  door  at  the  end  op- 
posite the  firebox.  The  present  arrangement  is  similar  in 
character  to  that  of  a  puddling  furnace. 

The  early  air  furnaces  were  very  small;  some  of  the 
first  are  said  by  Davis  on  the  authority  of  George  Belcher 
to  have  had  capacities  of  800  or  1000  pounds,  a  1500-pound 
charge  being  viewed  with  alarm.  Modern  furnaces  'have 
been,  continually  growing  in  size,  and  now  five-ton  heats 
are  unusual,  capacities  from  10  tons  to  15  tons  being  most 
common  in  practice.  Furnaces  have  been  built  and  oper- 
ated with  capacities  beyond  30  tons,  but  there  are  relatively 
few  in  use  with  capacities  far  above  20  tons. 

Design  Is  Simple 

The  construction  of  an  air  furnace  is  relatively  simple. 
Fig.  68  shows  an  air  furnace  in  side  elevation  and  cross  sec- 

The  furnace  walls  are  of  fire  brick,  usually  13  to  18 
inches  thick,  supported  and  enclosed  by  cast  iron  side  and 
end  plates  about  1  inch  thick.  The  'bottom  or  the  hearth 
A  is  built  of  silica  sand  or  more. rarely  paved  with  fire  brick. 
Coal  is  burned  in  the  firebox  B,  the  air  being  forced  through 
the  fire  by  a  blower  discharging  into  the  ash  pit  C ';  the  ash  pit 
doors  D  being  kept  closed.  Air  is  also  admitted  through  the 
tuyeres  E  to  complete  the  combustion  of  the  gas  and  flame  com- 
ing over  the  front  or  fire  bridge  Avail  F.  The  roof  of  the 


American   Malleable   Cast   Iron 


Air   Furnace    Melting  137 

furnace  consists  of  a  series  of  removable  fire  brick  arches, 
or  bungs,  supported  in  cast  iron  frames.  A  sufficient  number 
of  these  are  removed  to  permit  the  introduction  of  the  melt- 
ing stock. 

When  charging  the  furnace,  the  sprue  to  be  melted  is 
introduced  first  in  the  form  of  a.  layer  of  fairly  uniform 
thickness  extending  nearly  the  full  length  of  the  hearth. 
On  this  is  placed  malleable  or  steel  scrap,  the  latter  usually 
being  kept  well  forward  toward  the  front  bridge  wall.  Pig 
iron  is  placed  on  top  of  this  in  two  piles,  one  well  forward, 
the  other  further  back. 

Most  well  designed  furnaces  are  of  such  dimensions  as 
to  be  nearly  full  to  the  roof  when  a  heat  of  normal  size  is 
charged.  Care  therefore  must  be  taken  to  leave  an  oppor- 
tunity for  the  free  passage  of  flame  from  F  to  the  rear 
bridge  wall. 

The  bungs  are  then  put  on  and  firing  commenced.  The 
iron  soon  begins  to  heat,  naturally  first  at  the  top  and  in 
front.  The  firing  is  so  conducted  as  not  to  cause  much  melt- 
ing to  occur  until  the  lower  part  of  the  charge  is  well 
heated  through  to  a  gO'od  red. 

Of  the  ingredients  in  the  mix,  sprue  has  the  lowest 
melting  point,  pig  iron  next,  then  malleable  scrap,  and  steel 
the  highest.  The  melting  points  vary  inversely  as  the  com- 
bined carbon,  although  the  conclusions  are  slightly  compli- 
cated by  the  reabsorption  or  recombination  of  the  carbon  of 
malleable  scrap  below  the  melting  point. 

Through  the  courtesy  of  H.  W.  Highriter,  the  author 
has  been  furnished  data  as  to  the  recombination  of  carbon 
in  pig  iron  when  heated  under  circumstances  comparable 
with  melting  conditions.  The  data  'have  been  shown  graphi- 
cally in  Fig.  69.  Highriter  observes  a  rapid  increase  in  combined 
carbon  at  the  expense  of  graphitic  carbon  above  2000 
degrees  Fahr.  The  author  has  calculated  the  temperature  of 
the  solidus  for  the  observed  combined  carbon  and  plotted 
these  temperatures  in  a  dotted  line.  When  this  temperature 
falls  below  that  of  the  specimen,  incipient  fusion  has  com- 
menced. Melting  is  complete  when  the  temperature  reaches 
the  liquidus  which  is  dependent  on  the  total  carbon  and 
calculated  by  Highriter  as  2372  degrees  Fahr.  The  metal  by 

138  American   Malleable   Cast  Iron 

observation  fused  at  2362  degrees  Fahr.  It  will  'be  observed 
that  the  melting  point  referred  to  by  the  author  is  that 
where  melting  is  begun,  above  this  temperature  presumably 
the  graphite  is  rapidly  destroyed  by  solution. 

Moldenke  many  years  ago  published  data  as  to  the  re- 
lation between  combined  carbon  and  melting  point  of  cast 
iron  and  Dyer*  refers  to  the  same  facts. 

In  interpreting  the  author's  statements,  and  presumably 
Moldenke's  and  Dyer's,  confusion  between  the  beginning 
and  completion  of  melting  must  be  avoided. 

If  the  firing  is  properly  managed,  it  is  not  necessary  to 
melt  the  steel,  the  molten  pig  iron  dissolving  the  steel  as  it 
runs  down  before  the  steel  actually  melts.  Some  melters  ad- 
vocate introducing  the  steel  only  after  the  rest  of  the  charge 
is  melted. 

The  sprue  melts  fairly,  readily  even  under  all  the  other 
material  due  to  its  high  combined  carbon  content.  As  the 
iron  melts  the  surface  oxidizes  so  that  there  results  both  liquid 
iron  and  liquid  iron  oxide,  probably  Fe2O3.  The  latter  floats  on 
top  of  the  former  and  reacts  with  the  carbon,  silicon,  and 
manganese  of  the  metal,  oxidizing  those  to  CO2,  CO,  SiO2  and 
MnO  and  being  itself  reduced  to  FeO  almost  or  quite  com- 

The  oxides  of  manganese  and  iron  combine  with  the  silici 
to  form  an  acid  silicate  which  also  dissolves  some  of  the 
refractories  in  the  furnace  lining.  The  resulting  slag  .soon 
covers  the  surface  of  the  molten  metal  protecting  it  from 
further  action  of  the  furnace  gases. 

As  pools  of  iron  covered  with  slag  form,  a  good  melter 
will  endeavor  to  roll  unmelted  pig  iron  and  steel  into  these 
pools  so  as  to  bring  the  entire  charge  under  the  slag  blanket  as 
soon  as  possible,  thus  minimizing  oxidation  losses. 

The  flame  conditions  also  are  carefully  regulated  by  atten- 
tion to  the  dampers  in  the  blast  lines  to  the  firebox  and  top 
blast  tuyeres  and  by  keeping  the  openings  over  the  bridge  walls 
and  the  channel  or  neck  H  to  the  stack  of  the  right  dimensions. 

When  the  charge  is  all  melted  it  is  well  mixed  by  rabbling 
with  a  skimmer  bar.  The  slag  is  then  skimmed  off  by  raking 
*lron  Age,  Nov.  17,  1921. 

Air    Furnace    Melting 


it  out  through  the  skim  holes,  the  skimmer  bar  consisting  of  a 
1-inch  iron  bar  having  a  flat  plate,  say  %  x  3  x  9  inches 
affixed  by  its  center  to  the  end  of  the  round  bar.  The  other 
end  of  the  bar  is  bent  into  a  ring  to  form  a  handle. 

Meanwhile  the  fire  is  being  constantly  worked  with  a 
poker  to  keep  up  active  combustion.  The  heat  has  to  be  skim- 
med at  intervals  in  order  to  make  rapid  heating  possible 

Fig.  69. — Graph  showing  recombination  of  carbon  in  pig  iron 

and  also  to  keep  the  final  product  fairly  clean.  One  producer 
does  not  remove  the  slag,  but  drains  it  off  after  the  metal 
has  all  been  run -out  of  the  furnace. 

The  progress  of  the  heat  is  judged  as  to  temperatitre  and 
composition  by 'the  inspection  of  a  freshly  broken  surface  of  a 
not  too  rapidly  cooled '  sample  and  of  the  molten  metal  in  the 
ladle.  For  satisfactory  work  a  knowledge  of  the  composition 
of  previous  heats  also  is  necessary.  In  a  few  plants  more  or 
less  complete  preliminary  analyses  are  attempted  before  tapping. 
This  chemical  practice  is  attended  with  a  certain  amount  of  un- 


American   Malleable   Cast   Iron 

Air   Furnace    Melting  141 

certainty  as  to  further  changes  of  composition  between  sampling 
and  tapping  and  is  therefore  less  effective  than  the  correspond- 
ing practice  in  electric  melting.  When  the  metal  is  hot  and  of 
proper  composition  the  clap  stopper  in  the  tap  hole  /  is  cut 
through  and  the  metal  runs  out  in  a  stream  into  the  molders' 

In  the  early  days  of  the  art  the  profile  of  the  furnace 
roof  longitudinally  was  given  very  complex,  almost  fantastic 
curves.  These  usually  had  a  sharp  dip  in  the  roof  just  beyond 
the  front  bridge,  then  a  rise  forming  a  sort  of  hump  over  the 
hearth,  then  a  drop  toward  the  rear  bridge. wall  and  then  a  rise 
directed  toward  the  stacks. 

Furnaces  of  the  older  type  had  sloping  roofs  but  recently  the 
tendency  has  been  toward  a  nearly  straight  roof,  lower  at  the 
rear  bridge  than  at  the  front  and  sometimes  rising  again  into 
the  stack  as  a  matter  of  convenience.  A  modern  design  is 
shown  in  Fig.  70. 

The  flame  in  flowing  through  the  furnace  obeys  laws 
similar  to  those  governing  the  flow  of  water  in  channels. 
These  laws  'have  been  completely  investigated  by  Crum-Grzimai- 
lo  of  Petrograd,  (Stahl  und  Eiscn,  Dec.  7,  and  11,  1911),  who 
developed  the  mathematical  formulae  and  coefficients  applying 
to  the  problem  in  great  detail.  The  discussion  is  much  too 
technical  in  character  to  be  even  abstracted  here  beyond  the 
statement  that  the  laws  are  those  which  would  apply  to  the 
flow  of  one  fluid  through  another,  if  the  two  were  not  mixable 
and  differed  in  density  as  does  the  hot  flame  and  cold  at- 

This  investigation  coupled  with  a  knowledge  of  combustion 
and  temperature  conditions  to  be  expected  forms  the  only  logi- 
cal basis  for  furnace  design.  In  practice  actual  furnace  design 
is  generally  based  on  modifications  of  previous  designs.  This  is 
in  many  respects  sound  policy  as  tending  to  avoid  erratic  prac- 
tices. On  the  other  hand,  there  is  a  great  tendency  toward  per- 
petuation of  obsolete  features  inherent  in  such  a  process  of  ev- 

An  inspection  of  the  designs  of  many  furnaces  shows  a 
wide  variation  on  some  apparently  vital  points.  These  dif- 
ferences, however,  are  not  always  as  little  justified  as  may 


American   Malleable   Cast  Iron 

appear  on  the  surface  for  the  viewpoint  of   different  designers 
may  not  be  the  same. 

Thus,    for  example,   it   is   undoubtedly   sound   metallurgical 
practice  to  make  but  one  heat  a  day  on  a   furnace  and   make 

Fig.  71. — A  waste  heat  boiler  connected  to  two  air  furnaces.  Note  that 
coal    for    auxiliary    firing    is    on    hand 

that  a  very  large  one,  for  ithe  brger  the  capacity  the  greater 
is  the  melting  economy,  other  things  being  equal.  On  the 
other  hand,  consideration  must  be  given  to  the  space  re- 
quired for  molds,  to  the  physical  ability  of  the  men  to  pour, 

Air    Furnace    Melting 143 

etc-  Thus  it  is  that  this  practice  may  not  be  feasible.  If 
heats  are  required  at  given  time  intervals  it  may  be  more 
important  to  keep  the  time  schedule  correct  than  to  get  the 
maximum  of  economy,  hence  fuel  consumption  may  be  sacri- 
ficed to  melting  speed.  Such  a  consideration  also  may  limit 
the  practicable  size  of  heat.  Also  many  furnaces  are  built 
in  existing  buildings,  or  under  other  conditions  which  handi- 
cap the  designer  by  limiting  him  to  certain  dimensions  from 
these  causes. 

A  general  idea  of  the  usual  dimensions  of  air  furnaces 
can  be  gained  from  the  following:  The  volume  of  the  hearth, 
(the  volume  of  the  basin  below  the  level  of  the  skim  holes) 
is  directly  dependent  on  the  amount  of  metal  to  be  melted 
and  is  not  subject  to  any  discretion.  One  pound  of  melted 
cast  iron,  together  with  its  accompanying  slag  occupies  about  5 
cubic  inches;  therefore  10,000  cubic'  inches  of  hearth  must 
be  provided  for  each  net  ton  of  furnace  capacity. 

There  are  certain  practical  limits  to  the  depth  of  molten 
metal  in  the  hearth  which  can  be  successfully  worked.  Shal- 
low baths  presenting  to  the  flame  a  large  surface  per  unit 
weight  of  metal,  heat  easily  and  quickly  but  also  oxidize  easily 
and  quickly.  Extremely  deep  baths  are  difficult  to  heat,  but  the 
great  weight  per  unit  of  surface  favors  the  rapid  transfer  of 
heat  from  flame  to  metal  per  unit  of  hearth  area. 

Moreover,  large  capacities  coupled  with  shallow  baths  may 
involve  impracticable  dimensions.  Again,  the  bottom  of  the 
furnace  must  have  sufficient  slope  to  assure. complete  drainage 
to  the  tap  hole.  Even  in  unusually  short  furnaces  this  slope 
produces  a  difference  in  depth  at  the  tap  hole  and  rear 
bridge  of  perhaps  5  inches  so  that  an  average  depth  of  less 
than  2l/2  inches  is  not  workable  in  any  event,  because  it  neces- 
sitates a  "feather  edge"  of  metal  next  the  bridge. 

In  practice  the  average  depth  of  metal  ranges  from  about 
5  to  9  inches,  the  greater  depths  usually  occurring  in  furnaces 
of  the  greater  capacities.  The  depth  at  the  tap  hole  may  be 
from  2l/2  to  5  or  6  inches  greater  than  the  average  depth  de- 
pending largely  on  the  furnace  length.  These  depths  correspond 
to  hearth  areas  running  from  about  13%  square  feet  per  ton 
down  to  less  than  8  square  feet  per  ton. 

144 American  Malleable   Cast  Iron 

The  requirements  of  firing,  skimming,  etc.,  as  well  as  the 
maintenance  of  roof  arches  sets  a  maximum  inside  width  of 
between  5  and  6  feet  for  air  furnaces  of  the  usual  design,  a 
few  large  furnaces  of  special  design  have  a  clear  width  of  7 
feet.  When  the  maximum  width  is  reached  the  capacity  of  the 
furnace  can  be  increased  only  by  increasing  the  hearth  length. 
Extremely  shallow  baths  are  impracticable  when  large  capac- 
ities are  desired  because  they  necessitate  long  furnaces-  For 
example,  2Oto>n  furnaces  with  a  hearth  area  of  IS1/-*  square 
feet  per  ton  would  be  about  45  feet  long  between  the  bridge 
walls.  Hearths  from  14  to  27  feet  long  are  in  common  use, 
and  in  a  few  unusually  large  furnaces  they  are  several  feet 
longer.  A  certain  length  of  hearth  is  desirable  because  it 
insures  a  better  contact  of  flames  and  charge.  Excessive  lengths 
cannot  be  had  with  small  capacities  as  the  furnace  would  be 
too  narrow.  The  practicable  length  also  depends  on  the  fuel 
and  firing  conditions  since  a  length  which  does  not  allow  the 
flame  to  reach  to  the  rear  bridge  wall  is  unworkable. 

The  firebox  is  almost  fof  necessity  of  the  same  widths  as 
the  hearth.  The  grate  area  required  depends  on  the  rate  of 
combustion  of  fuel  desired  and  this  in  turn  depends  on  the 
furnace  capacity  and  on  the  relative  importance  of  quick  as 
against  economical  heating.  Air  furnace  grates  burn  from  43  to 
77  pounds  of  coal  per  hour  depending  on  firing'  conditions. 
Values  of  from  67  to  77  pounds  are  more  common  than  those 
near  the  lower  limit. 

Reported  tests  indicate  that  air  furnaces  use  from  slightly 
under  500  to  about  1200  pounds  of  coal  per  ton  of  charge. 
These  are  extreme  ranges*  the  usual  commercial  range  being 
from  750  to  900  pounds  per  ton,  depending  largely  on  the  size 
of  the  furnace-  These  figures  give  some  indication  of  grate 
areas  required  under  various  conditions,  having  in  mind  also  the 
fact  that  an  attempt  to  melt  rapidly  is  often  uneconomical. 
•  It  seems  to  be  usual  practice  to  provide  from  2  to  21/2  square 
feet  of  grate  per  ton  of  charge  although  a  number  of  fur- 
naces exceed  this  rate. 

Many  designers  do  not  agree  on  the  correct  height  of  an 
air  furnace  roof.  From  15  to  17  cubic  feet  per  ton  from 

Air    Furnace    Melting  145 

hearth  to  roof  are  unavoidably  necessary  in  order  to  accom- 
modate the  unmelted  charge.  This  sets  a  minimum  of  height 
for  any  given  hearth  area  per  ton  of  charge. 

Quantity   of  Air   Varies 

Almost  invariably  the  roof  slopes  downward  toward  the 
rear  bridge.  The  old  humpback  furnaces  had  a  somewhat  great- 
er average  height  than  the  more  modern  straight-roofed 
furnaces.  The  average  height  of  roof  above  the  metal  at 
the  side  walls  is  about  24  inches.  A  pound  of  ordinary  melt- 
ing coal  requires  about  12j4  pounds  of  air  for  combustion  under 
usual  operating  conditions.  The  relative  amount  of  air  entering 
the  furnace  through  the  top  blast  tuyeres  and  through  the 
grates  varies  in  practice,  but  the  average  ratio  seems  to  be 
about  28  to  100.  Therefore  a  pound  of  coal  requires  about 
10  pounds  of  air  through  the  grates  and  2j4  pounds  of  air 
through  the  top  blast  in  ordinary  operating  practice. 

The  firebox  is  operated  so  that  it  produces  a  poor  grade 
producer  gas  which  is  then  burned  with  a  sufficient  amount 
of  air  for  theoretical  combustion.  A  typical  gas  leaving  the 
firebox  is  composed  of  1.2  per  cent  oxygen;  8.0  carbon  dioxide; 
12.1  carbon  monoxide;  and  78.7  per  cent  nitrogen.  The  gas 
leaving  the  stack  contains  1.1  per  cent  oxygen;  12.7  carbon 
dioxide ;  3.6  carbon  monoxide ;  and  82.6  per  cent  nitrogen.  The 
analyses  take  no  account  of  the  water  from  the  combustion 
of  the  hydrogen  of  the  fuel.  The  oxygen  in  this  water  and 
that  used  in  the  oxidation  of  silicon  and  manganese  account 
for  the  relatively  high  value  of  the  nitrogen.  The  flame  gases 
also  contain  unburned  hydrocarbons  of  unknown  character  and 
amount  which  escape  sampling. 

Any  attempt  to  further  reduce  the  carbon  monoxide  content 
by  adding  additional  oxygen,  probably  would  result  in  a  pro- 
hibitively high  excess  of  oxygen  in  the  gas,  causing  heavy 
oxidation  during  the  melting  process.  • 

The  mechanism  of  this  oxidation  has  already  been  re- 
ferred to  as  consisting  of  the  oxidation  of  the  iron  to  the  Fe2O3 
followed  by  the  subsequent  reduction  of  the  Fe2O3  to  FeO 
by  the  silicon,  carbon  and  manganese  of  the  bath.  The  amount 
of  oxidation  varies  widely  depending  upon  the  furnace  at- 

146 American  Malleable  Cast  Iron 

mosphere  and  similar  conditions.  Over  an  extended  period, 
however,  it  seems  nearly  constant  for  any  successfully  operat- 
ing plant.  The  losses  expressed  in  percentage  of  the  total 
weight  of  original  charge  and  in  percentage  of  the  amount 
of  each  element  present  are  generally  about  as  follows: 

Table   V 


Total  amount 

Total     charge  of    element 

100  -per  cent  100  per  cent 

Carbon      0.62  15.8 

Silicon    0.33  31.4 

Manganese    0.26  48.1 

Phosphorus 0.00  0.00 

Sulphur    —0.01  —22.2 

Iron                                                   1.14  1.2 


The  results  of  the  figures  in  the  second  column  form  an  in- 
teresting comparison  of  the  "oxidizability"  of  the  different  ele- 
ments when  melted  in  an  acid  furnace. 

Oxygen   Absorbed   During   Melting 

A  more  interesting  method  of  clearly  showing  the  relative 
affinity  for  oxygen  of  the  different  metals  is  to  calculate  the  oxy- 
gen combined  with  each  one  of  the  elements  during  melting. 
This  calculation  has  been  made  using  the  preceding  data  and 
the  results  are  shown  in  the  table  below.  In  the  first  column 
is  shown  the  oxygen  combined  with  each  of  the  four  oxidiza- 
ble  elements  in  terms  of  the  weight  of  original  charge  and  in 
the  second  column  in  terms  of  the  weight  of  the  oxidized  ele- 
ment present  in  the  charge. 

Table  VI 


Element  present  in 

Total    charge  original    charge 

100  per  cent  100  per  cent 

Carbon    1.60  50 

Silicon     0.38  36 

Manganese     0.06  11 

Iron    .....     0.32  34 


Air   Furnace   Melting  147 

It  will  be  seen  that  carbon  combines  much  more  greedily 
with  oxygen  than  any  other  element,  silicon  coming  next,  man- 
ganese oxidizing  much  less  readily  and  iron  only  slightly.  Of 
course  the  results  would  differ  with  variations  in  gas  com- 
position and  furnace  lining. 

It  will  be  seen  that  the  melting  process  oxidizes  a  total  of 
2.34  per  cent  of  the  original  charge,  and  combines  there  with 
oxygen  weighing  2.36  per  cent  of  the  original  charge.  There 
should  thus  result  a  weight  of  slag  equal  to  2.5  per  cent  of  the 
metal  charged  and  of  gas  equal  to  2.2  per  cent  of  the  metal 
charged,  were  there  no  contamination  from  molten  refractories. 
A  typical  sample  of  air  furnace  slag  showed  the  following  com- 
position : 

Analysis   of   Air   Furnace    Slag 

Per   cent 

FeO     28.80 

Fe2O3    1.16 

MnO    4.85 

Si02    (etc)    50.42 

A12O3 14.77 


The  metallic  oxides  aggregate  34.81  per  cent  of  the  weight  of 
the  slag.  From  the  preceding  tables,  this  corresponds  to  13.8 
per  cent  SiCX.  Therefore  the  above  slag  consists  of  a  mix- 
ture of  58.70  per  cent  oxidation  products  and  41.30  per  cent 
molten  refractories  and  since  the  weight  of  slag  oxidation  prod- 
ucts was  computed  to  be  2.5  per  cent  of  the  weight  of  the 
charge  the  actual  slag  weight  should  be  slightly  more  than 
4.2  per  cent  of  the  original  metal  charged  into  the  furnace.  It 
is  not  assumed  that  these  data  are  absolutely  correct  but  they 
furnish  a  fair  guide  to  what  may  be  expected  in  practice. 

Refractories   Destroyed   by   Melting 

Since  every  ton  of  iron  melted  destroys  34  pounds  of  re- 
fractories by  melting,  it  is  evident  that  frequent  furnace  repairs 
are  necessary.  The  furnace  parts  most  strongly  exposed  to 
heat  usually  are  relined  at  intervals  of  from  10  to  20  heats. 
The  roof  over  the  hearth  lasts  usually  from  16  to  24  heats 
and  the  sand  bottom  from  10  to  20  heats.  In  one  instance  the 
writer  saw  a  furnace  make  34  heats  without  relining,  and 


American   Malleable   Cast  Iron 

Fig.    72. — Gray   sprue;    characteristic    of    high    carbon    and    silicon   and 

sometimes  of  low  pouring  temperature   (full  size) 

Fig.       73. — Gray       sprue       showing      white       patches;       characteristic 
of    less    but    still    excessive    carbon    and    silicon.      Note    "in- 
verted   chill,"    i.e.    greater    grayness    near    the    surface 

than    at   center    (full   size) 

Fig.    74. — Moderately   mottled   sprue;    characteristic   of   carbon,    silicon 
and    temperature   suited    to    small   work    (fulj    size) 

in  another  saw  a  bottom  last   120  heats  as  a  result  of  careful 
attention.    However,  this  record  is  believed  to  be  exceptional. 

The  charge  going  into  the  furnace  can  be  computed  by 
adding  to  the  final  composition  wanted  the  expected  melting 
losses  and  then  arranging  a  mixture  from  the  available  melting 
stock  conforming  to  these  requirements-  The  process  is  one 

Air   Furnace   Melting 


Fig.    75. — Normal    sprue    for    metal    of    the    higher    carbon    ranges    of 
specification   metal   in  average   work.   Note  leaf-shaped   bright 

crystal    facets   radiating  from    center    (full    size) 
Fig.   76. — Similar   to   Fig.    74  but  lower  in   carbon.     Note  decrease   in 

leaf-shaped    crystals    (full    size) 

Fig.  77. — Similar  to  Fig.  76  but  quite  low  carbon.     Note  finely  gran- 
ular   fracture   from   which   the  leaf-shaped    crystal    has   almost 

-  disappeared    (full  size) 

Fig.  78. — "High"  iron,  i.e.  metal  low  in  carbon,  silicon  and  manganese; 

fracture    granular  -throughout    and    edge    showing    blowholes 

(full    size) 

of  simple  arithmetic  and  the  great  mystery  made  of  the  matter 
by  the  older  melters  was  not  justified. 

However,   the  -skill    of '  the   melter    is   important   in   main- 

150  American   Malleable   Cast   Iron 

taming  furnace  conditions  so  that  the  oxidation  losses  are  uni- 
form and  as  small  as  practicable.  The  appearance  of  the  flame 
in  the  furnace,  the  eddy  currents  in  the  bath  and  the  appear- 
ance of  the  slag,  whether  viscous  or  liquid,  indicate  to  the 
skillful  melter  what  is  going  on  in  the  furnace.  Similarly  the 
color  and  fluidity  of  the  metal  and  the  appearance  of  the  frac- 
ture after  cooling  permit  of  close  inferences  regarding  its 

Interpreting    Appearance    of    Fracture 

Among  the  more  obvious  indications  of  the  fracture  are 
the  presence  of  graphitic  areas  or  mottles  indicative  of  too 
high  a  silicon  or  carbon  or  both,  larger  leafy  crystals  radiat- 
ing from  the  center  indicating  moderately  high  carbons  de- 
creasing to  very  fine  granular  structures  as  the  carbon  falls 
to  near  2  per  cent.  There  also  is  the  rim  of  fine  blow  holes 
and  the  spray  of  oxidizing  iron  arising  from  the  surface  of  the 
metal  in  cases  of  "burnt"  heats  very  low  in  silicon. 

The  actual  conditions  are  not  even  capable  of  illustration 
photographically  since  some  of  the  fractures  do  not  show  up 
clearly  except  by  looking  at  them  in  light  falling  in  various 

It  can  be  shown  that  by  far  the  largest  part  of  the  oxida- 
tion losses,  occurring  in  practice,  is  complete,  when  the  metal 
is  melted  down  and  ready  to  skim. 

From  the  time  the  iron  is  all  melted,  before  skimming,  un- 
til the  moment  of  tapping  no  marked  changes  of  composition 
occur  as  to  carbon  and  manganese  although  the  silicon  will 
decrease  perhaps  0.1  per  cent  during  the  removal  of  the  first 
slag.  This  presupposes  a  properly  operated  furnace. 

Composition  May  Vary  During  Heat 

Samples  taken  from  the  last  of  a  heat  frequently  show 
a  considerably  lower  carbon,  silicon  and  manganese  content 
than  those  taken  at  the  first  of  the  heat.  However,  this  is  due, 
not  to  a  progressive  oxidation  which  would  have  affected  the 
entire  heat  to  that  extent  had  it  been  left  in  the  furnace,  but 
to  the  effect  of  oxidation  on  the  very  thin  layer  of  metal 

Air   Furnace    Melting 


left  in  the  furnace  as  the  last  metal  is  being  withdrawn.  Only 
a  small  weight  of  metal  is  of  a  composition  different  from 
the  bulk  of  the  heat.  A  feature  that  frequently  is  misunder- 
stood is  the  elimination  of  graphite.  Often  it  is  supposed 
that  the  fact  that  the  longer  the  heat  is  left  in  the  fur- 

Fig.    79. — Changes    of    metal    after    tapping 

nace  the  lower  the  graphite  is  due  to  oxidation  of  carbon  and 
silicon.  As  a  matter  of  fact  the  elimination  of  graphite  is 
largely  a  function  of  the  pouring  temperature  and  time,  and 
metal  will  show  progressively  clearer  fractures  during  the 
progress  of  the  pouring  of  a  heat  without  any  accompany- 
ing change  of  ultimate  chemical  composition.  Fig.  79  shows 
such  a  condition. 

In   this   figure  the   composition   of   the   metal   with   respect 
to    total    carbon,    graphitic    carbon,    silicon    and    manganese    is 

152  American  Malleable  Cast  Iron 

shown  for  samples  in  the  form  of  1^-inch  sand-cooled  cyl- 
inders poured  at  intervals  of  three  minutes  each  while  the  heat 
was  running  out  of  the  furnace.  It  should  be  said  in  ex- 
planation that  this  was  not  a  normal  malleable  iron  heat  but 
one  for  a  special  class  of  work  requiring  great  perfection 
of  surface  on  castings  on  thin  sections,  hence  the  high  values  of 
silicon  and  carbon.  However,  the  curve  shows  strikingly  the 
rapid  decrease  in  combined  carbon  as  the  metal  is  exposed  longer 
to  high  temperatures. 

Temperature  of  Furnace 

Temperature  conditions  in  air  furnaces  are  not  accurately 
established.  The  metal  flowing  from  the  spout  has  a  tem- 
perature from  2100  to  2500  degrees  Fahr,  as  measured  by 
radiation  pyrometers.  Such  determinations  involve  a  correction 
for  coefficient  of  radiation  since  clean  metal  does  not  radiate  heat 
as  rapidly  as  would  a  theoretical  black  body.  The  use  of  optic- 
al pyrometers  involves  a  similar  correction  for  emissivity  which 
is  however  of  much  smaller  magnitude.  Optical  pyrometer 
measurements  coupled  with  observations  of  metal  at  known 
temperatures  suggest  that  true  values  are  probably  more  nearly  from 
2500  to  2700  degrees  Fahr.  and  that  the  radiation  coefficient 
is  not  well  established.  The  flame  in  the  neck  when  the 
heat  is  melted  has  a  temperature  of  about  2500  degrees.  The 
furnace  roof  and  the  flame  under  it  seem  to .  reach  temper- 
atures up  to  3000  degrees  or  somewhat  higher,  the  average 
being  about  2800  degrees.  In  the  firebox  the  temperatures 
are  about  the  same  as  in  the  neck,  2500  degrees,  Fahr.  The 
latter  figures  are  probably  more  accurate  than  those  on  the 
flowing  metal  since  black  body  conditions  are  more  nearly 
approached.  They  are  if  anything  somewhat  low. 

The  following  heat  balance  gives  a  general  idea  of  fuel 
consumption  in  an  air  furnace.  Since  there  is  considerable 
variation  in  furnace  practice  the  correction  of  heat  values 
for  the  actual  temperature  of  fuel  and  air  entering  the  fur- 
nace was  believed  an  unnecessary  refinement. 

While  based  only  on  estimates,  this  balance  gives  a  fairly 
comprehensive  idea  of  what  becomes  of  the  heat  delivered 

Air   Furnace    Melting  153 

Table  VII 


B.t.u.  per      B.t.u.  per 

ton  ton 

charged       charged 

Heat  value  coal  burned 11,200,000 

Heat    from    oxidation    of    charge 219,400 

Heat  of  formation  of  basic   silicates 30,000 

Total  11,449,400 

Latent  and  sensible  heat  of  metal 878,940 

Sensible  heat  of  flue  gas 6,112,000 

Loss  to  incomplete  combustion  of  C  to  CO  only     1,232,000 

Evaporation  of  water  in  coal 10,000 

Heat  value  of  unburned  combustible  in  ash 37,335 

Sensible  heat  of  slag 42,000 

Latent  heat  of  slag  (est.)    30,000 

Sensible   heat   of  furnace    structure 600,000 

Radiation  conduction  and  unaccounted   for 2,507,125 

Totals 11,449,400     11,449,400 

to  the  melting  furnace.     The  values  may  be  summarized  on  a 
percentage  basis  shown  in  Table.  VIII. 

This  indicates  clearly  that  the  larger  part  of  the  waste  is 
in  the  sensible  heat  of  the  flue  gas.  This  heat  occasionallv 
is  recovered  by  the  use  of  waste  heat  boilers  which  gen- 
erate steam  with  the  heat  of  the  gases  leaving  the  furnaces. 
The  difficulties  encountered  are  largely  of  a  steam  engineering 
character  and  arise  from  the  intermittent  supply  of  heat  avail- 

Prof.  Touceda  in  a  paper  before  the  American  Foundry- 
men's  Association  in  1920,  has  given  tentative  suggestions  for 
the  utilization  of  waste  heat  from  air  furnaces.  These  sug- 
gestions are  for  various  double  hearth  furnaces  in  which  the 
waste  heat  from  one  hearth  is  used  to  preheat  the  charge  in 

Table  VIII 


Per  cent  Per  cent 

Heat  value  of  coal  fired. .  .    100               Heat  in  metal 7.81 

Heat     from     reactions     in                        Heat  in  flue  gas . .  54.70 

furnace 2.2            Heat   in   slag 0.64 

Incomplete    combustion..  11.30 

Heating  furnace  walls. .  . .  5.35 

Radiation  and  conduction  22.40 

Total  input 102.2  Total    output     102.20 

154 American  Malleable  Cast  Iron 

the  other.  The  mechanical  means  are  somewhat  complicated 
involving  movable  hearths  and  also  somewhat  continuous  op- 
eration. From  a  thermal  viewpoint,  however,  they  are  most 

Reference  has  been  made  to  the  use  of  forced  draft-  in 
air  furnaces.  The  air  supply  is  usually  at  low  pressure, 
about  4  ounces  per  square  inch,  although  a  few  plants  use 
pressures  of  a  pound.  In  such  cases  the  furnaces  must  be 
equipped  with  doors  at  the  fire  'hole  and  skim  holes.  At 
least  one  important  producer  operates  on  natural  draft  alone, 
using  no  blowers  and  consequently  no  top  blast.  This  partic- 
ular plant  depends  on  extremely  high  stacks.  Many  air 
furnace  stacks  are  from  45  to  85  feet  high,  and  have  internal 
diameters  from  24  to  48  inches.  The  lack  of  agreement  is 
unaccountable  except  on  the  basis  of  poor  design.  Nearly 
all  air  furnace  stacks  have  capacities  far  beyond  their  actual 

It  has  been  stated  in  the  general  discussion  of  fuels  that 
both  oil  and  pulverized  coal  fuel  have  been  tried  in  air  fur- 
nace practice.  As  far  as  the  author  knows,  the  use  of  oil 
never  has  been  generally  satisfactory,  owing  to  difficulties 
in  maintaining  the  proper  furnace  atmosphere,  free  from  excess 
of  air  or  CO2. 

The  chemical  changes  in  melting  depend  entirely  upon 
the  temperature  and  composition  of  gas  in  contact  with 
the  metal.  The  use  of  producer  gas  entailed  similar  diffi- 
culties and  was  never  commercially  adopted,  except  of  course 
in  open-hearth  practice.  Similar  difficulties  have  been  encoun- 
tered in  the  use  of  pulverized  coal  but  have  been  successfully 
overcome,  at  least  by  a  few  combustion  engineers. 

A  successful  equipment  of  this  character  is  shown  in  Fig. 
80  and  consists  of  a  hopper  containing  the  pulverized  fuel  pro- 
vided with  screw  conveyors  for  feeding  a  stream  of  coal 
into  the  current  of  air  from  the  blower  shown  in  the  lower 
right  hand  corner  of  the  picture.  The  ends  of  the  con- 
veyor shafts  are  shown  under  the  numbers  1-2-3-4-5  painted 
on  the  hopper. 

The  current  of  air  loaded  with  coal  dust  enters  the 
furnace  through  three  burners  in  the  head  wall  of  the  fire 

Air   Furnace   Melting 


box,  which  is  blocked  up;  and  through  two  burners  through 
the  roof  at  the  point  where  the  top  blast  usually  enters. 
By  proper  manipulation  of  the  relative  supply  of  coal  and 
air  to  these  several  burners,  proper  control  may  be  main- 
tained and  satisfactory  working  insured.  The  entire  problem 

Fig.    80. — A    po'.vclercd    coal    attachment    for    an    air    furnace 

is  merely  the  design  of  a  burner  capable  of  so  feeding  the 
fuel  into  the  air  as  to  maintain  uniform  combustion  conditions 
with  coal  and  air  supply  capable  of  regulation  through  a  fairly 
wide  range. 

Such  a  set  of  burners  operated  to  duplicate  furnace  atmos- 
pheres corresponding  to  the  best  air  furnace  practice  will 
produce  results  superior  in  control  and  economy  to  results 
under  hand  firing.  The  improvement  results  primarily  from 
the  constancy  of  ratio  of  coal  to  air  throughout  the  heat,  thus 

156 American   Malleable   Cast   Iron ^ 

avoiding  the  losses  due  to  alternately  incomplete  combustion 
and  excess  air  w'hich  occur  even  with  the  best  hand  firing 
when  the  average  condition  is  perfectly  controlled. 

.    Table   IX 


Metal  charged 

Fe  .1901.3 
C     62.0 
Si    21.6 
Mn    11.0 
S    0.9 
P   3.2 

Coal         Air    tories 



[olten  metal 
Slag  Flue  gas 

1878.5  22.8    
49.6    ...     617.0 
15  0    66    





"5.6  '.'.'.'.'.   '.'.'. 

5.8    5.2    
1.1     1.2        2.0 


.  34.0 
....   1918.0    ... 
....   7243.0    ... 

....   15.0  1903.0 


'.'.','.     '.'.'.     '  'l4.0 

Total.  2000.0  Ibs.  688.0  9161.0  34.0  11,883.0         1953.2  84.8  9818.0  27.0 

The  author  has  seen  the  results  of  many  tests  on  this 
type  of  equipment  but  it  is  doubtful  whether  data  have  yet 
been  accumulated  which  warrant  a  definite  conclusion  as  to 
economy  of  operation  due  to  pulverized  fuel. 

The  tests  which  he  has  seen  seem  to  indicate  that  the 
requirements  as  to  furnace  atmosphere  are  such  that  no  direct 
saving  on  coal  is  practicable.  The  economies  may  rather  be 
expected  to  result  from  decreased  labor  and  refractory  costs, 
and  greater  independence  in  using  poor  coal. 

The  data  at  hand  point  also  to  a  lower  and  much  more 
constant  loss  by  oxidation  of  the  several  metals  than  is  nor- 
mal to  ordinary  air  furnace  practice,  but  insufficient  experience 
is  available  to  be  sure  whether  this  condition  always  exists. 

As  a  skeleton  outline  of  the  metallurgy  involved  in  the 
operation  of  an  air  furnace  the  outline  of  the  chemical  changes 
shown  in  Table  IX  may  be  interesting.  The  summary  is  typical 
only  and  does  not  necessarily  apply  exactly  to  any  given  case. 

The  summary  is  based  on  the  weights  of  each  material 
and  each  element  entering  into  the  reactions  for  one  net  ton 
of  charge. 

Air  furnaces  usually  are  operated  by  a  crew  of  either 
two  or  three  men  exclusive  of  those  doing  the  charging. 

Air    Furnace    Af  citing  157 

bringing  in  fuel  and  stock,  etc.  The  majority  of  air  fur- 
naces make  a  heat  in  20  to  30  minutes  per  ton  plus  about 
one  half  hour  if  the  furnace  is  hot  to  begin  with,  or  plus 
one  and  one  half  hours  if  the  furnace  is  cold  at  the  start  of 
the  melting  operations. 

Large  furnaces  melt  faster,  per  ton,  than  small  ones, 
but  large  heats  still  take  longer  to  make.  It  is  said  that  one 
plant,  using  oil  fuel  made  heats  around  30  tons  in  three  and 
one  half  or  four  hours,  although  the  writer  is  not  prepared  to 
vouch  for  this  statement.  Another  plant  making  heats  of 
this  size  with  coal  runs  16  to  18  hours  to  a  heat,  it  is  said. 

In  most  plants  skimming  begins  when  the  heat  is  well 
melted  which  will  be  from  one  and  one  half  to  two  hours 
before  the  heat  is  ready.  In  a  plant  where  instead  of  skim- 
ming the  slag  is  tapped  out  after  the  iron  is  poured  it  is 
claimed  that  no  loss  of  time  or  fuel  is  incurred  due  to  this  meth- 
od. The  operation  is  on  fairly  large  furnaces.  In  spite  of 
the  obvious  desirability  of  this  operation,  if  practicable,  it  has 
not  been  adopted  elsewhere.  The  author  does  not  know 
whether  or  not  this  conservatism  is  justified.  The  feeling  seems 
to  be  one  of  suspicion  as  to  the  general  economy  and  practica- 
bility of  the  operation. 



PRACTICALLY   the  only   radical   change  in  melting   prac- 
tice  which   has   been   introduced   into   the  malleable   indus- 
try in  the  last  half  century  is  the  use  of  electric  furnaces. 
So  far  only  one  producer  operates  under  this  method,  which  is 
protected  by  patents  covering  the  conditions  necessary  to  com- 
mercial   success. 

In  electric  operation,  increased  accuracy  of  chemical  con- 
trol is  made  possible  and  the  success  of  the  melting  operation 
is  largely  independent  of  variations  in  quality  of  stock  and  fuel 
and  of  blast  and  similar  conditions.  The  belief  that  electric 
melting  is  adopted  because  it  permits  the  manufacture  of  al- 
loys of  compositions  unattainable  in  the  air  furnace  is  not 
founded  on  fact.  While  it  is  possible,  for  example,  to  make 
iron  as  low  as  .017  per  cent  in  sulphur,  if  desired,  there  is 
no  engineering  advantage  in  such  an  operation. 

Electric  melting  as  practiced  today  is  conducted  by  the 
triplex  process,  developed  by  W.  G.  Kranz,  which,  as  the  name 
indicates,  is  conducted  in  three  distinct  stages.  This  process 
supplements  the  advantages  of  the  electric  furnace  with  the 
use  of  a  cupola  and  a  bessemer  converter  to  assist  the  elec- 
tric furnace  in  operations  to  which  it  is  not  so  well  suited. 
The  rationale  of  the  process  is  as  follows : 

The  electric  furnace  alone  is  suitable  for  melting  or  heating 
metal  with  slight  contact  with  air  or  any  other  substance  ex- 
cept the  furnace  lining  and  slag.  Therefore,  it  is  suited  rather 
to  keep  the  composition  of  its  contents  unaltered  than  to  make 
changes  in  composition. 

Chemical  changes  occur  therein  only  as  a  consequence  of 
the  addition  of  various  alloys  of  slag-making  ingredients  and 
the  effect  of  such  additions  can  be  quantitatively  controlled.  The 
changes  of  chemical  composition  easiest  of  attainment  in  the 
electric  furnace  are  increases  in  silicon,  manganese,  or  phos- 
phorus and  decreases  in  sulphur  and  oxygen.  Carbon  can  be 
added  or  removed,  or  silicon  removed  with  greater  difficulty 


American   Malleable   Cast   Iron 

but   the   removal   of   phosphorus    is   not   practicable   under   the 
usual  operating  conditions   in   malleable   melting. 

'Whereas  the  electric  furnace  is  an  expensive  source  of  hear 
energy,   the  cupola   is   the   cheapest   known   method   for   merely 

Fig.    81. — Cupola    producing    molten    iron — The    starting    point    of    the 
Kranz    triplex    process 

melting  cast  iron,  composition  being  no  object.  .  Cupola  melt- 
ing always  removes  at  least  part  of  the  silicon  and  manganese 
and  adds  sulphur,  leaving  the  phosphorus  unaltered.  The  car- 
bon content  is  nearly  independent  of  the  mix  used  depending 
only  on  the  condition  of  the  fuel  bed.  The  carbon  content 
always  is  relatively  high. 

Electric    Furnace    Melting  161 

The  bessemer  converter  furnishes  an  easy  and  economical 
way  to  remove  all  carbon  silicon  and  manganese  from  iron  but 
adds  a  great  deal  of  oxygen. 

The  three  units  form  an  ideal  team,  each  possessing  good 
qualities  to  supplement  the  weak  points  of  its  mates.  The 
cupola  furnishes  cheaply  a  supply  of  liquid  iron  of  high  and 
approximately  constant  carbon  content  which  readily  can  be 
controlled  as  to  its  maximum  silicon,  manganese  and  phos- 
phorus  content,  but  may  have  high  sulphur  from  the  fuel. 
Carbon,  silicon  and  manganese  can  be  removed  from  this 
metal  in  the  bessemer  converter,  although  oxygen  may  be 
added.  By  taking  the  proper  relative  amounts  of  cupola  and 
bessemer  metal  a  mixture  can  be  produced  having  a  'carbon 
content  close  to  any  desired  value,  and  which  also  is  below 
any  desired  fixed  values  in  silicon,  manganese  and  phosphorus. 
However,  it  contains  an  indefinite  and  relatively  large  amount 
of  sulphur  and  oxygen. 

This  molten  mixture  can  be  given  its  final  heating  in  the 
electric  furnace  without  too  great  expense,  and"*.iby  the  use  of 
suitable  slags  the  sulphur  and  oxygen  can  be  removed  without 
any  -effect  on  the  silicon,  manganese,  or  phosphorus.  Guided 
by  the  analysis  of  the  molten  charge,  silicon  and  manganese 
can  be  added  to  adjust  these  values  as  desired  and  a  product- 
made  without  prohibitive  cost,  adjusted  to  chemical  specifica- 
tions on  each  of  the  five  common  elements  and  freed  from 
oxygen.  . 

These  are  the  steps  in  the  Kranz  process,  which  since 
passing  through  the  experimental  stage  in  1913-1914  has  pro- 
duced many  thousands  of  tons  of  malleable  cast  iron  in  two  plants 
of  the  largest  producer  of  malleable  in  the  world.  The  proc- 
ess as  outlined  comprises  melting  in  the  cupola ;  decarburizing  in 
the  converter;  heating,  desulphurizing  and  deoxidizing  and 
raising  the  manganese  and  silicon  in  the  electric  furnace;  and,  if 
desired,  adding  sulphur  in  the  ladle.  For  still  greater  uniform- 
ity it  was  once  suggested  that  the  cupola  and  converter  metal 
be  stored  in  a  mixer  prior  to  its  introduction  into  the  electric 
furnace,  but  practice  has  proved  that  this  step  is  not  nec- 

It  has  been  found  that  a  product  varying  from  dead  soft 


American   Malleable   Cast  Iron 

steel  to"  gray  iron,  and  including  alloy  steels  can  be  made  by 
this,  process  at  the  will  of  the  operator.  If  dephosphorization 
is  desired,  for  example  in  steel-making,  an  extra  step  is  re- 
quired in  the  electric  furnace,  involving  the  formation  of  a 
dephosphorizing  slag  and  its  removal  before  proceeding  with 
the  desulphurizing  and  deoxidizing. 

Fig.    82. — Two-ton    side-blow    converter    producing    liquid    steel    from 
cupola    metal    in    triplex    process 

Metallurgy    of    Triplex   Process 

It  may  be  well  to  consider  the  individual  steps  involved 
in  greater  metallurgical  detail.  In  general,  the  melting  stock 
consists  of  sprue  and  malleable  scrap  and  high  silicon  pig  iron. 
The  mix  is  calculated  only  to  be  close  to  the  desired  value  in 
silicon  content.  The  manganese  automatically  remains  low  and 
with  a  little  care  the  phosphorus  can  be  kept  below  about  0.19 
per  cent,  which  is  all  that  is  required. 

Electric    Furnace    Melting  163 

It  is  intended  that  the  cupola  metal  shall  run  slightly  under 
1  per  cent  silicon.  Too  low  a  value  causes  trouble  from  gum- 
ming' up  the  cupola  taphole  and  spout  and  the  ladle.  The  maxi- 
mum is  determined  by  the  metal  to  be  made.  The  composition 
of  the  metal  leaving  the  cupola  under  ordinary  working  condi- 
tions is  approximately  as  follows:  Carbon,  3.10;  silicon,  0.80  to 
0.95;  manganese,  0.12  to  0.19;  sulphur,  0.09  and  up,  and  phos- 
phorus, 0.14  to  0.19  per  cent.  The  dimensions  of  the  cupola 
are  such  as  to  allow  the  unit  to  run  continuously  to  produce 
the  metal  required  by  the  electric  furnaces.  Interruptions  and 
intermissions  are  undesirable  because  they  affect  the  tempera- 
ture of  the  fuel  bed  and  consequently  the  carbon  content. 

The  ratio  of  iron  to  coke  in  the  cupola  may  average  7  to 
1,  varying  somewhat  with  operating  conditions.  Two  cupolas 
are  provided  and  are  used  alternately  to  permit  repairs. 

'i  he  converter  easily  reduces  the  molten  metal  to  a  composi- 
tion about  as  follows :  Carbon,  0.20  and  under ;  silicon,  trace ; 
manganese,  trace;  sulphur,  0.12  and  up;  and  phosphorus,  0.17 
per  cent  and  up.  A  considerable  oxidation  of  iron  also  occurs, 
which  together  with  the  mechanical  loss  in  the  form  of  fine 
drops  amounts  to  from  8  to  15  per  cent  of  the  converter  charge. 
If  a  carbon  content  of  say  2.60  per  cent  is  desired,  cupola  and 
converter  metal  in  the  ratio  of  240  to  50  will  be  required  and  the 
mixture  will  have  a  composition  as  follows:  Carbon,  2.60;  sili- 
con, 0.66  to  0.78;  manganese,  0.10  to  0.16;  sulphur,  .095  and 
up;  and  phosphorus  0.14  to  0.19  per  cent. 

Since  each  furnace  heat  is  handled  as  a  unit,  it  will  be  seen 
that  the  converter  charge  is  dependent  on  the  capacity  of  the 
electric  furnace  and  the  carbon  content  of  the  cupola  metal.  In 
the  illustration  chosen  the  converter  must  deliver  50/290  or 
about  17  per  cent  of  the  capacity  of  the  electric  for  each 
blow.  The  metal  introduced  must  exceed  this  amount  by  the 
expected  oxidation  and  mechanical  losses. 

The  electric  furnaces  actually  in  use  have  a  rated  capacity 
of  six  and  15  tons,  respectively  so  that  when  working  at  capac- 
ity the  converter  would  have  to  deliver  1.02  and  2.35  tons 

The  electric  furnaces  used  are  of  the  Heroult  type,  operat- 
ing on  3-phase,  alternating  current.  The  6-ton  units  consume 

164 American   Malleable   Cast  Iron 

800  kilovolt-amperes  of  power  at  80  to  100  volts  and  the  15 -ton 
units  from  18,000  to  22,000  kilovolt-amperes  at  from  90  to 
110  volts. 

Handling  Charge  in  Furnace 

The  internal  diameter  of  the  larger  units  is  approximately 
10  feet.  In  all  cases  the  bottoms  are  dolomite  and  the  lining 
of  the  side  walls  magnesite.  The  molten  metal  is  introduced 
into  the  furnace,  the  arc  formed,  and  a  lime  slag  made  on  the 
surface.  The  slag-making  ingredients  are  lime,  fluorspar  and 
coke;  in  amounts  determined  by  the  working  conditions  and  not 
by  weight.  About  150  pounds  of  lime  and  coke  and  100  pounds 
of  fluorspar  may  be  used  in  a  12-ton  heat,  the  active  ingredient 
of  the  resulting*  slag  being  calcium  carbide,  CaC2.  The  ac- 
tual amounts  of  slag-making  ingredients  are  however  not  de- 
termined by  weight  but  by  the  appearance  of  the  slag  and 
the  "operating  conditions  of  the  furnace.  This  carbide  reacts 
energetically  with  any  metallic  oxides  present.  For  instance 

3    FeO   +  CaC2  =  GaO   -f   3    Fe  +  2    CO 

No  appreciable  amounts  of  CaC2  are  formed  until  the  oxy- 
gen is  practically  completely  eliminated.  At  that  stage  the 
elimination  of  sulphur  begins,  the  products  being  CaS  and 
carbon,  which  dissolves  in  the  metal.  This  process  can  not 
be  conducted  under  any  but  a  reducing  condition  for  CaS 
is  easily  oxidized  to  CaO,  the  sulphur  unfortunately  not  burn- 
ing to  SO2  but  dissolving  in  the  iron.  This  introduces  certain 
difficulties  in  lowering  the  silicon  content.  For  example  silicon 
is  easily  and  almost  quantitatively  oxidized  by  ore,  the  reaction 
presumably  being 

Si  +  2  FeaO3  =  SiO2  +  4  FeO 

Unfortunately  the  FeO  of  the  resulting  slag  immediate- 
ly reacts  as  follows : 

FeO  +  CaS  =  FeS  +  CaO 

and  the  desulphurizing  must  be  recommenced.  The  removal 
of  silicon  can  be  conducted  in  this  way,  but  it  is  a  cause 
of  difficulty  in  the  maintenance  of  the  desired  slag. 

Fortunately  the  high  carbon  alloys  occurring  in  malle- 
able practice  do  not  take  up  carbon  from  the  carbide  slags 
used  to  any  appreciable  extent,  nor  does  the  CaC2  reduce  a 

Electric    Furnace    Melting  165 

considerable  amount  of  silicon  from  any  calcium  silicates  which 
may  be  present. 

A  sample  is  taken  for  analysis  after  the  metal  is  thor- 
oughly mixed  in  the  furnace  and  should  show  a  correct 
amount  of  carbon  and  phosphorus,  and  a  deficiency  in  sili- 
con and  manganese.  These  latter  two  elements  are  added  as 
ferrosilicon,  ferromanganese,  Spiegel  or  similar  alloys.  Carbon 
can  be  added  as  pig,  cupola  iron,  or  in  very  'hot  heats  as  coke 
or  can  be  reduced  by  steel  additions.  Silicon  can  be  removed 
with  ore  as  previously  described  but  it  is  not  intended  that  this 

Fig.    83.— Transfer    train   consisting   of   electric   motor    car   and    trailer 

with  crane  ladle.     This   equipment  is  used  in  carrying  cupola 

and    converter    metal    to    the    electric    furnaces 

be  done  in  regular  practice.  The  removal  of  phospohrus  from 
malleable  heats  is  so  expensive  that  it  is  cheaper  to  scrap  such 
heats  than  to  attempt  to  correct  them. 

Temperature  Limited  by  Operations 

The  temperature  to  which  electric  metal  can  be  heated 
depends  only  on  the  refractories  used  and  in  commercial  prac- 
tice is  from  2600  to  3000  degrees  Fahr.  The  figures  are  by 
radiation  pyrometer  and  in  the  writer's  judgment  are  likely 
to  be  lower  than  the  correct  values.  More  recent  data  by  optical 
pyrometer  show  temperatures  from  2900  degrees  to  3000  de- 
grees Fahr.  It  appears  therefore  that  the  figures  around  2600 

166 American   Malleable   Cast   Iron 

degrees  arose  from  an  improper  correction  for  coefficient  of  ra- 
diation. The  relative  merits  of  the  two  systems  of  pyrometry 
have  been  discussed  in  connection  with  air  furnace  melting.  It  is 
customary  to  take  a  heat  away  in  one  or  two  large  ladles  and  to 
proceed  immediately  with  another  heat.  The  advantages  of  the 
process  already  have  been  pointed  out  and  all  point  back  to  ac- 
curacy of  control.  The  most  serious  limitation  is  the  expensive 
first  cost  of  the  melting  installation,  which  places  it  beyond  the 
reach  of  the  small  producer.  Furthermore  the  process  is  not 
suited  to  intermittent  operation  involving  the  banking  of  cupolas 
and  filling  of  electric  furnaces  with  coke.  To  obtain  success- 
ful results  a  24-hour  day  during  the  working  week  is  neces- 
sary. Counting  iy2  hours  per  heat  or  16  heats  per  day  and 
allowing  for  some  loss  of  time  for  repairs  between  heats,  and 
bearing  in  mind  possible  reductions  in  economy  where  very 
small  units  are  used,  a  simple  calculation  will  indicate  that  suc- 
cessful operation  can  be  had  only  in  plants  of  fair  capacity. 

The  two  plants  now  in  operation  are  equipped  with  three 
small  and  two  large  furnaces,  respectively,  and  are  intended 
to  operate  on  large  tonnages.  Furthermore,  the  crane  service 
required  for  the  handling  of  hot  metal,  etc.,  almost  precludes  the 
introduction  of  hot  melting  into  any  but  an  especially  built  plant, 
thus  further  limiting  its  general  introduction. 

All  this  is  in  addition  to  the  limitations  to  the  general  use 
of  the  process  due  to  its  control  through  patent  protection.  Fur- 
nace repairs  are  relatively  much  less  frequent  in  electric  fur- 
naces than  in  air  furnaces.  The  bottom  is  taken  care  of  after 
each  heat.  The  magnesia  side  walls  and  silica  roof  each  last 
from  120  to  240  heats,  while  the  basic  bottom,  being  repaired 
after  each  heat,  lasts  indefinitely. 

The  cost  of  heat  in  the  electric  furnace  is  high,  but  on  the 
other  hand  the  utilization  of  heat  reaches  an  extremely  high 
efficiency  owing  to  the  elimination  of  the  losses  in  fuel-fired 
furnaces  arising  from  the  escape  of  the  hot  products  of  com- 
bustion. The  current  is  on  about  one  hour  for  each  heat. 

Charging,  tapping  and  patching  consume  up  to  45  min- 
utes of  time.  Cupolas  are  intended  to  run  a  week  on  each 
lining  but  usually  are  repaired  at  24  to  72-hour  intervals. 

Electric    Furnace    Melting  167 

The  converters  are  of  the  side-blown  type  of  a  capacity 
suited  to  the  Heroult  furnace  they  serve  and  are  lined  with 
ganister.  Converter  bottoms  last  about  a  week,  and  the  tops 
nearly  indefinitely. 

It  will  be  instructive  to  follow  quantitatively  the  chemical 
changes  occurring.  The  following  analysis  is  typical  of  the 
slag  produced  by  the  cupola. 

Per    cent 

SiO,    -52.90 

A1,O,     12.80 

FeO      5.10 

FeaO 00 

MnO 2.60 

CaO 21.30 

MgO     3.70 

S    0.20 

Undetermined    and  .error     1.40 


This  is  practically  a  mixture  of  molten  refractory  and 
limestone,  little  oxidation  of  the  metal  having  occurred  under 
the  strongly  reducing  conditions  of  the  cupola. 

Assuming  that  the  cupola  charge  consists  of  10  per  cent 
silicon  pig,  sprue  and  malleable  scrap,  the  two  latter  averaging 
0.70  silicon,  in  order  to  have  a  mixture  at  1.10  silicon  the  mix 
will  contain  4.3  per  cent  pig  iron  and,  for  example,  40  per 
cent  sprue  and  55.7  per  cent  malleable  scrap.  The  average 
analysis  of  such  a  mixture  figures  out  carbon,  2.68; 
silicon,  1.10;  manganese,  0.27;  sulphur,  055  and 
phosphorus,  0.177  per  cent.  This  metal,  when  melted 
and  leaving  the  cupola  has  a  composition  of  carbon,  3.10;  sili- 
con, 0.85;  manganese,  0.15;  sulphur,  0.09  and  phosphorus,  0.177 
per  cent.  This  change  of  composition  coupled  with  the  pre- 
viously given  slag  analysis  amounts  to  a  net  loss  by  oxidation 
of  0.166  per  cent  of  the  total  weight  charged. 

The  oxidation  of  silicon,  manganese  and  iron  is  nearly 
balanced  by  the  gain  in  sulphur  and  carbon  from  the  fuel.  In 
practice  there  is  a  loss  of  noticeable  magnitude  due  to  me- 
chanical causes.  By  calculation  the  slag  corresponds  to  5.8  per 
cent  of  the  weight  of  the  charge;  1684  per  cent  is  derived 
from  oxidation  of  the  metal ;  25  per  cent  from  the  lime- 
stone added  as  a  flux ;  and  the  balance  from  the  fusion  of  the 


American   Malleable   Cast   Iron 

furnace  lining,  coke  ash,  impurities  in  stone,  etc.  Assuming 
the  limestone  to  have  been  90  per  cent  CaCO3,  the  weight  of  the 
limestone  added  was  about  50  per  cent  of  the  slag  weight  or 
2.9  per  cent  of  the  weight  of  metal  charged.  The  limestone 
lost  to  the  flue  gas  an  amount  of  CO2  equal  to  11  per  cent  of 
the  slag  weight. 

When   the   cupola  metal   is   blown   in   the   converter   it   be- 

Fig.    84. — Heroult    electric    furnace    in    which    cupola    and    converter 
metal    is    charged    for    final    step    in    triplex    process 

comes  a  steel  containing,  for  example:  Carbon,  0.10;  sulphur, 
0.095;  and  phosphorus,  0.187  per  cent.  The  slag  formed  has  a 
composition  of  which  the  following  is  typical : 

Per    cent 

SiO3     57.50 

A12O3    1.43 

FeO     34.41 

Fe,O, 1.45 

M-nO     3.80 

OaiO     0.25 

M-gO     0.34 

Error    and    undetermined     0.82 


Electric    Furnace    Melting  169 

A  loss  in  weight  of  5.36  per  cent  of  the  weight  charged 
into  the  converter  is  indicated.  In  practice  a  larger  loss  is 
noted  due  to  mechanical  losses  and  to  considerable  amounts 
of  iron  oxide  which  escape  as  fume  and  are  not  taken  into  ac- 
count in  the  analysis. 

The  slag  is  equivalent  in  weight  to  4.86  per  cent  of  the 
metal  charged.  Of  this  slag  50.08  per  cent  is  an  oxidation  prod- 
uct of  the  metal  and  49.92  per  cent  is  fused  refractory. 

In  the  electric  furnace  no  oxidation  takes  place,  the  only 
elements  affected  being  sulphur  and  oxygen  which  leave  the 
metal  to  become  calcium  sulphide  and  carbon  monoxide,  respec- 
tively. The  former  remains  in  the  slag,  while  the  latter  escapes 
as  a  gas.  Therefore  the  slag  in  the  electric  furnace  is  not  in 
any  material  degree  derived  from  the  elements  in  the  iron,  but 
depends  for  its  quantity  and  largely  for  its  composition  on  the 
slag  forming  additions  used.  These  are  lime  (CaO)  fluor- 
spar (CaF2)  and  coke.  The  supposition  is  that  the  coke  and 
lime  form  .calcium  carbide  which  removes  both  sulphur  and 

However  the  slags  never  are  nearly  pure  mixtures  of  CaC2 
and  CaF2.  Typical  slag  obtained  under  conditions  which  would 
possibly  have  destroyed  "any  CaC2  by  the  action  of  the  atmos- 
pheric moisture  had  a  composition  as  follows : 

Per    cent 

SiO, 29.80 

A1,O3    2.85 

FeO     0.50 

Fe2O3     nil 

M.nO     0.18 

CaF2     0.70 

CaO    44.51 

MigO    7.55 

CaiS 7.20 

Undetermined     '6.71 


From  the  behavior  of  the  slag  it  seems  reasonable  that 
most  of  the  lime  is  combined  with  silica  and  that  there  is  but 
little  free  CaO  as  Ca(OH)2  either  normally  present  or  derived 
from  the  decomposition  of  carbides.  Possibly  the  CaO  from 
these  sources  may  run  to  5  per  cent  or  similar  undetermined 


American   Malleable   Cast   Iron 

Possibly  the  MnO  s'hown  is  MnS  floating  up  from  the  met- 
al, in  which  case  the  CaS  would  be  reduced  and  CaO  increased 
to  allow  for  the  S  combined  with  Mn.  The  fluorine  apparently 
is  largely  eliminated  in  the  furnace.  Data  as  to  slag  quan- 
tities are  uninteresting  as  having  no  connection  with  the  metal- 
lurgical principles.  The  additions  may  amount  in  the  aggre- 
gate to  perhaps  1  or  1.5  per  cent  of  the  weight  of  the  metal. 

Fig.  85. — Heroult  furnace  tilted  for  pouring 

Metallurgy   of   the   Slag 

Assuming  a  desulphurization  of  .07  per  cent,  the  slag 
composition  referred  to  and  excluding  sulphur  from  the  coke 
amounts  to  around  44  pounds  of  slag  per  ton  of  metal.  Of 
the  slag  the  SiO2  A12O3  and  MgO  are  primarily  derived  from 
the  furnace  lining.  Those  comprise  40.2  per  cent  of  the  en- 
tire slag.  Therefore  for  each  ton  of  metal  17.6  pounds  of  re- 
fractory are  melted  and  26.4  pounds  of  slag  is  formed  from 
lime,  fluorspar  and  carbon  and  from  the  metal  itself.  Of  the 
ingredients  from  the  metal  the  principal  item  in  weight  is  1.4 

Electric    Furnace    Melting  171 

Table  X 



In   pounds   per    ton    of  cupola   charge 
From  From 

In  cupola  cupola  converter 

charge  coke  air  Total 

C    .  53.6  8.3  61£ 

Si   22.0 

Mn   5.4 

P    3.54 

S     1.10  0.7 

O    ...  ..       0.60*  *  0.60 

Fe    1914.36  1914.36 


In  electric  To  electric 

In  final    In  cupola     In  con-       In  con-      furnace         furnace 
product          slag  verter  slag  verter  gas        slag    atmosphere 

C 51.90  ...  ..Q>  10.0  0.00* 

Si    14.17  5.0  2.83  '.  .  .  0.00* 

Mn     2.46  2.4  0.50  .  .  .  0.04 

P 3.54  ...  ...  ...  0.00* 

S  0.08  ...  ...  ...  1.00 

O    ...*  ...*  ...*  ...*  0.60 

Fe    1904.84  4.8  4.60  ...  0.12 

*Includes    only    those    amounts    at    some    stage    alloyed    with    the 
molten    metal. 

pounds  of  sulphur,  the  MnO  and  FeO  being  only  about  0.3 
pounds  per  ton.  •  Deducting  these  two,  the  slag  has  24.7 
pounds  of  material  per  ton  of  metal  derived  from 
the  slag-forming  additions.  All  of  these  figures  men- 
tioned are  to  be  considered  as  suggestive  only.  A 
balance  sheet  of  the  elements  concerned  in  the  triplex  process  is 
shown  in  Table  X.  It  must  be  understood,  however,  that  the 
process  has  not  been  quantitatively  investigated  to  the  point 
where  all  the  reactions  are  clearly  worked  out.  The  figures  in 
the  balance  sheet  for  oxygen  are  merely  estimates.  The  sulphur 
data  are  not  based  on  a  complete  series  of  tests,  but  are  in 
accord  with  current  practice.  The  table  neglects  oxygen  in  ori- 
ginal metal  and  final  product.  Ferromanganese  and  ferrosilicon 
are  not  supposed  to  be  added.  If  charged  into  the  electric, 
these  alloy  quantitatively  with  the  charge. 

Heat    Balance    of    Triplex   Process 

A  heat  balance  for  the  triplex   process  is  extremely  inter- 
esting as  giving  an  insight  into  the  character  of  heat  losses  re- 


American  Malleable   Cast  Iron 

Table  XI 


B.t.u.  B.t.u. 

Heat  value  fuel 3,718,000 

Total  heat,  metal 1,692,000 

Sensible    heat,    slag 63,800 

Sensible  heat,  flue  gas 180,000 

Heat  value  of  Fe,  CO  in  flue  gas 744,000 

Radiation  and  unaccounted  for 1,038,200 

Total   output 3,718,000 


Total    heat    of   metal    charged 282,000 

Heat  of  combustion   of   C,    Si,    Mn 93,400 

Total     input             375,400 

Total   heat,   metal    292,800 

Sensible    heat,    slag , 10,900 

Sensible  heat,  gas  and  undetermined 71,700 

Total    output 375,400 

Electric   Furnace 

Total    heat    metal    charged 1,690,800 

Heat  equivalent  of  electric  input 564,200 

Total    input 2,255,000 

Total  heat,   metal 1,865,000 

Sensible  heat,  slag 23,000 

Radiation  and  undetermined   367,000 

Total   output 2,255,000 

maining.  Unfortunately  the  results  of  complete  tests  of  the 
process  including  all  the  factors  involved  are  not  available.  Also 
the  heat  of  formation  of  some  of  the  compounds  entering  into 
the  reaction,  more  particularly  in  the  electric  furnace  are  not 
known.  In  the  absence  of  this  information  the  following  bal- 
ance has  been  built  up  on  estimates  from  other  sources  of  the 
composition  of  gas  leaving  the  cupola  and  converter,  and  of 
the  temperature  of  the  cupola  gas,  and  of  the  metal  at  various 
stages.  Also  the  heat  of  formation  of  the  slag  has  not  been 
considered  a  source  of  energy  nor  has  allowance  been  made 
for  the  latent  heat  of  fusion  of  slags  and  refractories. 

The  presence  of  oxygen  in  the  metal,  at  various  stages  has 
not  been  followed  quantitatively  so.  that  no  account  of  the 
thermal  effect  of  the  formation  and  reduction  of  FeO  can  be 
taken.  The  latter  items  are  included  among  the  undetermined 

Electric    Furnace    Melting  173 

Table   XII 


B.t.u.  B.t.u. 

Heat    value    of    coke 3,718,000 

Heat    value    of    current 564,200 

Heat  combination  of  Fe  Si,  Mn  and  C 93,400 

Total    heat    input 4,375,600 

Incomplete    combustion    in    cupola.  .  .  .  .x 744,000 

Sensible  heat,  slag : 63,800 

Sensible  heat,   flue  gas 180,000 

Radiation    and    undetermined 1,038,200 

Total    cupola    loss 2,026,000 

Sensible   heat,   converter   slag. 10,900 

Sensible  heat,  gas  and   undetermined 71,700 

Total   converter   loss 82,600 

Ladle  loss  by  radiation    (preheated  ladle) 12,000 

Sensible  heat,  slag 23,000 

Radiation  and  undetermined 367,000 

Total    heat,    metal 1,865,000 

Total     output      4,375,600 

losses  at  the  various  stages  of  the  process.  However,  the 
balance  in  Table  XI,  based  on  one  ton  of  metal  charged  into 
the  cupola  and  on  temperatures  above  atmospheric  may  be 
regarded  as  indicative  of  the  major  items. 

The  cupola  utilizes  45.5  per  cent  of  the  heat  of  the  fuel. 
The  converter  delivers  77.7  per  cent  of  the  total  heat  sup-, 
plied,  using  11.5  per  cent  of  the  heat  of  combus- 
tion of  the  'elements  burned  in  further  heating  the 
metal.  The  ladle  loss  in  transferring  the  metal,  not 
shown  above,  amounts  to  less  than  1  per  cent.  The  electric 
furnace  delivers  in  the  metal  82.7  per  cent  of  all  the  heat 
furnished  it,  using  30.9  per  cent  of  the  thermal  equivalent  of 
the  electric  input  in  heating  the  metal. 

Heat  Balance  in  Per  -Cent 

A  summary  of  the  heat  balance  based  on  the  process  as  a 
whole  appears  in  Table  XII.     The  tabulation  may  be  condensed 

174 American   Malleable   Cast  Iron 

somewhat    further   and   expressed   in   percentages    of    the    total 
heat  supplied  by  fuel  and  power  as  follows : 

— Per  cent — 

Heat    of    combustion    fuel     86.5 

Heat    equivalent    of    power     13.5 

Heat    of    combustion    of    elements    in    converter  2.2 

Heat    loss    in    cupola    47.3 

Heat    loss     in    converter 1.9 

Heat    loss    in    ladle     0.3 

Heat  loss  in  electric  furnace 9.1 

Total    heat    metal  43.6 

Totals     102.2       102.2 

The  figures  show  the  relatively  very  great  thermal  effi- 
ciency of  the  process  as  compared  with  air  furnace  or  open- 
hearth  melting.  A  heat  made  from  cold  stock  in  the  electric 
furnace  would  show  a  still  hig'her  thermal  efficiency,  approxi- 
mating that  of  the  electric  furnace  alone.  This  would  not,  how- 
ever, correspond  to  a  greater  economic  efficiency  in  view  of  the 
greater  cost  of  a  'heat  unit  as  electric  energy  than  as  coke. 

From  the  viewpoint  of  fuel  consumption  a  vast  consideration 
of  the  electric,  furnace  is  not  complete  without  pointing  out  that  a 
consumption  of  21/2  pounds  of  coal  per  kilowatt-hour  is  an  ex- 
tremely economical  figure,  attainable  only  in  unusually  large 
turbine-driven  plants. 

There  would  be  superimposed  on  this  further  transformer 
and  line'  losses  so  that  the  electric  furnace  may  get  from  4 
per  cent  to  8  per  cent  of  the  energy  of  the  boiler  fuel  as 
electric  energy. 

This  consideration,  coupled  with  the  high  overhead  for  the 
powder  plant,  accounts  for  the  great  cost  of  heat  energy  derived 
from  electric  power  as  compared  with  that  of  an  equal  amount 
of  heat  energy  potentially  present  in  the  fuel. 



IX    ADDITION    to    air   and    electric    furnace    melting,    which 
was  discussed  in  Chapters  VII  and  VIII,  there  are  two  com- 
mercial methods  of  melting  malleable.     That  which  employs 
the  cupola  can  he  dismissed  with  a  few  words,  since  its  use  for 
producing  specification  metal  has  been  prohibited  by  the  specifica- 
tions of  the  American  Society  for  Testing  Materials  since  their 
first   revision. 

The  objections  to  cupola  metal  are  based  on  lack  of  uni- 
formity of  product  and  lack  of  control.  Because  of  construc- 
tion of  the  cupola  and  its  method  of  operation,  no  large  amount 
of  liquid  iron  is  accumulated  at  one  time;  therefore  there  is  no 
assurance  that  successive  taps  will  be  even  nearly  the  same  in 
composition  unless  the  charge  consists  of  only  one  material, 
which  manifestly  is  impracticable. 

These  variations  are  of  no  consequence  in  the  general  run 
of  gray  iron  castings,  but  in  malleable  practice  with  its  much 
reduced  practicable  range  of  composition  they  are  prohibitive, 
especially  for  large  work.'-  Furthermore,  since  the  cupola  runs 
continuously  for  several  hours  there  is  no  means  of  judging  the  fit- 
ness of  the  iron  for  its  intended  purpose  either  by  analysis  or 
fracture  before  it  is  poured. 

Control  of  Metal  Limited 

Even  when  the  best  possible  uniformity  is  secured  the  cu- 
pola process  has  limitations  of  control  which  render  it  unsuitable 
in  the  production  of  a  general  run  of  malleable  castings.  The 
molten  iron  runs  down  through  a  mass  of'  incandescent  coke, 
meeting  in  the  spaces  between  the  coke  a  stream  of  gas, 
originally  air,  but  converted  by  the  fuel  into  a  mixture  of  car- 
bon dioxide,  carbon  monoxide  and  nitrogen. 

Under  any  given  operating  condition,  especially  as  to  tem- 
perature, a  definite  equilibrium  exists  which  determines  the  com- 
position of  the  products  of  combustion  in  contact  with  mean- 


American   Malleable   Cast 


Cupola  and  Open  Hearth  Melting  177 

descent  carbon  at  that  temperature.  The  descending  liquid  iron 
thus  passes  into  a  zone  in  which  temperature  and  gas  composi- 
tion are  adapted  to  equilibrium  with  molten  iron  of  only  one 
specific  carbon  content  and  capable  of  adding  or  removing  car- 
bon easily  if  the  metal  comes  down  lower  or  higher  than  this 
value  in  equilibrium  with  the  gas  phase.  Therefore  a  cupola 
produces  metal  of  a  carbon  content  almost  independent  of  that 
of  the  charge  and  dependent  solely  on  the  combustion  conditions. 
The  possible  range  of  working  conditions  is  such  as  to 
produce  metal  containing  from  about  2.70  to  3.25  per  cent  carbon 
— a  value  too  high  for  the  production  of  a  high  class  product 
except  in  small  work.  The  sulphur  content  of  cupola  metal  also 
is  invariably  high  in  view  of  the  intimate  contact  of  molten 
metal  and  fuel. 

Some  cupola  metal  made  for  extremely  small  work  thus  is 
converted  into  white  heart  malleable,  possibly  without  the  full 
understanding  of  the  operator,  and  the  work  is  annealed  by  de- 
carbonization  of  the  thin  sections  and  not  by  graphitization. 

The  surviving  successful  application  of  the  cupola  process 
to  black  heart  malleable  is  in  the  manufacture  of  pipe  fittings 
where  the  product  usually  does  not  have  the  greatest  possible 

The  metallurgy  of  cupola  melting  has  been  considered  in  Chap- 
ter VII  in  connection  with  the  triplex  process.  However,  a 
higher  fuel  ratio  is  common  in  ordinary  cupola  melting  than  in 
the  triplex  process  because  the  iron  must  leave  the  cupola  at  a 
higher  temperature  in  order  to  run  into  molds  than  if  it  is  to  be, 
handled  only  by  a  crane  ladle. 

A  ratio  of  metal  to  fuel  of  between  4  to  1  and  6  to  1  may 
represent  operating  practice,  and  this  represents  the  one  great 
advantage  of  the  cupola — cheapness  both  of  construction  and 
operation,  the  utilization  of  heat  being  about  two  or  two  'and 
one-half  times  as  efficient  as  in  the  air  furnace. 

Open-hearth  melting,  especially  when  large  tonnages  and 
continuous  operation  are  involved,  should  be  a  desirable  method 
of  operation.  That  its  practice  is  confined  to  relatively  few 


American   Malleable   Cast   Iron 







Cupola  and  Open  Hearth  Melting 179 

plants  may  be  due  to  the  conservatism  of  the  industry  and  to 
the  tonnage  limitation. 

In  general,  the  open-hearth  furnaces  used  in  the  malleable" 
industry  are  similar  in  construction  to  those  used  in  steel  making 
and  in  size  represent  the  lower  limits  of  capacity  used* in  that 
industry.  Some  experimental  heats  have  been  made  in  basic 
furnaces  but  acid-lined  furnaces  apparently  are  used  for  com- 
mercial operation. 

The  melting  operation  is  similar  in  principle  to  aar  furnace 
melting,  except  in  the  application  of  the  heat. 

Furnaces  ranging  in  capacity  from  5  to  20  tons  have  been 
used,  the  larger  units  being  preferred  when  practicable.  The 
furnace  roofs  are  of  silica  brick  and  the  bottoms  of  silica  sand. 
The  regenerative  system  upon  which  the  operation  depends  is 
so  well  known  as  hardly  to  require  description.  The  products  of 
combustion  leaving  the  hearth  pass  through  checkers  of  fire 
brick  and  impart  their  heat  to  these  brick.  When  the  brick  is 
thoroughly  heated  the  direction  of  gas  passage  is  reversed,  the 
air  being  drawn  into  the  furnace  through  the  previously  heated 
checkers.  The  products  of  combustion  pass  out  through  check- 
ers at  the  opposite  end  of  the  furnace.  When  producer  gas 
is  used  it  also  is  preheated.  The  incoming  air  gradually  cools 
the  hot  set  of  checker  work  while  the  products  of  combustion 
heat  the  checker  at  the  outlet  end  when  the  latter  grow  hot  the 
direction  of  passage  is  again  reversed,  this  operation  being 

Using   Heat   of   Flue   Gases 

The  period  of  reversal  depends  upon  the  heat  capacity  of 
the  checker  work  and  in  ordinary  design  a  reversal  every  15  to 
30  minutes  may  be  contemplated.  The  object  is  to  utilize  the 
sensible  heat  of  the  flue  gases.  The  gases  leaving  the  iron  can- 
not impart  heat  thereto  unless  their  temperature  is  above  that  of 
the  metal.  However,  their  heat  can  be  imparted  to  the  furnace 
content  by  using  it  to  preheat  the  air  and  sometimes  the  fuel 
used  before  the  combustion  begins.  In  this  way  a  higher  furnace 
temperature  and  lower  heat  loss  are  maintained. 

The  heat   loss   depends   upon   the   temperature   of    the   out- 


American   Malleable   Cast   Iron 


Cupola  and  Open  Hearth  Melting 



4)    C  <*«    O    M 

^  !3 

cj  jn< 
rt  •= 
G  H 

jc     -^rt  £  o  ^  0-5 

S-  ^Ilil1 

s  SS'sIl  s 

-    S 

-a  Z       X 

182 American   Malleable   Cast  Iron 

going  gases  and  this  in  turn  upon  the  volume  of  the  regenerator 
chambers  and  the  period  of  reversals.  In  theory  the  outgoing 
temperature  might  be  reduced  to  that  of  the  incoming  air  and 
gas  but  this  is  practically  impossible. 

Campbell  states  that  open-hearth  steel  furnaces  should  be 
capable  of  operation  without  the  stack  gases  attaining  a  red  heat. 
However,  this  result  is  not  often  attained.  Assuming  this  red 
heat  to  be  900  degrees  and  the  gas  composition  to  be  the  same 
as  in  air  furnace  melting  the  sensible  heat  of  the  out-going  gases 
is  only  9/25  of  that  of  the  air  furnace,  counting  from  0  degree 
Fahr.  as  a  basis  (which  is  not  strictly  correct).  Therefore  the 
heat  value  saved  in  the  regenerators  is  17/25  of  that  lost  in 
the  stack  in  air  furnace  practice.  Using  the  heat  loss  in  sensible 
heat  of  gases,  leaving  the  air  furnace  as  7800  B.t.u.  per  pound 
of  coal,  and  counting  again  from  0  degrees  Fahr.,  the  heat  saved 
per  pound  of  coal  would  be  5304  B.t.u.  or  over  one-third  the 
heat  value  of  the  fuel. 

Quoting  Campbell  in  Manufacture  and  Properties  of  Struc- 
tural Steel>  for  a  given  sized  chamber  the  escaping  gases  are 
a  certain  number  of  degrees  hotter  than  the  gases  that  go  into  it. 
If  this  difference  is  300  degrees,  then  if  the  entering  gas  is  400 
degrees,  the  escaping  gases  will  be  700  degrees,  and  if  the  en- 
tering gases  are  700  degrees  the  outgoing  gases  will  be  1000 
degrees.  It  will  be  seen  that  this  reasoning  implies  that  no 
change  of  economy  results  from  changes  of  temperature  in  pro- 
ducer gas  passing  from  the  producer  to  the  furnace.  If 
no  heat  is  lost  in  the  gas  while  passing  from  the  producer  to 
the  regenerator  a  loss  corresponding  to  this  saving  is  incurred 
in  the  outlet  gases. 

Since  open-hearth  furnaces  are  much  less  common  in  the 
malleable  industry  than  air  furnaces,  correspondingly  less  is 
known  of  their  design  and  operation.  For  general  information 
on  open-hearth  operation  the  interested  reader  is  referred  to 
the  literature  of  the  subject  regarding  steel  melting. 

By  kindness  of  Messrs.  Lanihan  and  Fulton;  the  writer  has 
been  given  access  to  a  certain  amount  of  data  accumulated  in 
the  successful  operation  of  open-hearth  furnaces  by  the  Fort 

Cupola  and  Open  Hearth  Melting 183 

Pitt  Malleable  Iron  Co.,  Pittsburgh.  Much  of  what  follows  is 
based  on  that  practice  supplemented  where  necessary  by  con- 
clusions drawn  from  other  sources. 

Malleable  melting  in  the  open  hearth  differs  metallurgically 
in  one  essential  respect  from  steel  melting.  The  steel  maker 
operates  to  greatly  reduce  the  carbon  and  silicon  content  of  the 
bath  by  oxidation.  In  malleable  practice  this  oxidation  must 
be  kept  down  as  much  as  practicable  to  insure  control  and  re- 
duce melting  losses.  Therefore  the  furnace  atmosphere  is  sub- 
ject to  the  same  limitations  as  to  composition  as  in  air  furnace 
practice.  In  view  of  the  fact  that  this  oxidation  is  actually  kept 
down  to  about  the  same  limits  as  in  air  furnace  practice  it  seems 
reasonable  in  the  absence  of  direct  figures  to  assume  that  the  CO, 
CO2,  O  and  N  in  the  products  iof  combustion  should  be  about 
the  same  as  is  given  in  Chapter  VI.  An  essential  difference, 
however,  will  be  the  presence  of  a  greater  proportion  of  steam 
or  water,  since  these  furnaces  are  operated  on  natural  gas  and 

In  the  chapter  on  air  furnace  melting,  the  flue  gas  analysis 
was  given  as  oxygen,  1.1;  carbon  dioxide,  12.7;  carbon  mon- 
oxide, 3.6;  and  nitrogen,  82.6  per  cent.  Assuming  the  gas  in 
the  present  case  to  have  this  composition  and  assuming  that  the 
formula  of  the  petroleum  is  Cn  H2n  +  2  the  ratio  of  C  to  H 
in  the  fuel  will  vary  from  3  to  1  to  6  to  1,  depending  on  the 
molecular  weight  of  the  hydrocarbon  being  burned.  We  can 
calculate  the  flue  gas  per  pounds  of  fuel  closely. 

Assuming  a  ratio  of  C  to  H  of  5  3/4  (which  probably  is  a 
little  high  but  will  compensate  for  the  inaccuracy  introduced 
by  neglecting  the  carbon  burned  from  the  metal)  we  may  con- 
clude that  one  pound  of  fuel  will  require  nearly  17.1  pounds  of  air 
for  combustion,  yielding  18.1  pounds  of  gas  made  up  of  the 
following  amounts  of  the  several  constituents: 


<?• .152 

£0,    2.430 

CO     435 

H2o  .'..'.'.'::::::::::  1:322 

N    13.76 

184  American   Malleable   Cast   Iron 

If  a  gas  analysis  were,  the  water  would  not  be  found, 
being  condensed  to  a  liquid  in  sampling  for  analysis.  The  com- 
position by  volume  apparently  would  be : 

Per  cent 

O    0.8 

CO,    9.7 

CO     2.8 

N    ,  ..86.7 

Total 100.0 

In  the  absence  of  actual  analyses  this  may  be  taken  as 
representing  a  near  approach  to  the  combustion  conditions  to  be 
expected  using  oil  fuel.  The  differences  using  gas  fuel  are 
probably  insignificant  as  compared  with  the  probable  inac- 
curacies in  some  of  the  assumptions  made. 

The  chemical  changes  occurring  in  the  bath  are  identical  in 
character  and  similar  in  magnitude  to  those  occurring  in  the  air 

The  oxidation  losses  in  open-hearth  melting  have  been  in- 
vestigated, in  the  light  of  the  changes  of  composition  during  the 
process  as  determined  at  the  Fort  Pitt  foundry.  Typical  re- 
sults are  given  both  in  per  cent  of  the  original  charge  and  in  per 
cent  of  the  original  amount  of  the  element  present : 

Loss  in  Open-Hearth  Melting 

Total  charge         Amount  of  element 

100  per  cent 






Total    2.51 

It  will  be  noted  that  the  oxidizing  conditions  are  similar  to 
those  encountered  in  air  furnace  practice  and  described  under 
that  heading.  The  gain  in  sulphur  and  loss  of  carbon,  silicon 
and  manganese  are  less  in  open-hearth  practice  than  in  air  fur- 
nace practice.  However  the  oxidation  of  iron  is  sufficiently 
greater  to  keep  the  net  loss  at  nearly  the  same  figure  as  in  air 


100  per  cent 
...   0  49 


0  154 



—  004 

Fc    . 

.    1.58 

Cupola  and  Open  Hearth  Melting 185 


These  conditions  can  be  further  followed  by  a  consideration 
of  the  composition  of  open-hearth  slag.  A  representative  sample 
of  this  material  had  the  following  analysis : 

Per  cent 

FeO  37.6 

Fe,03     2.7 

MnO    3.87 

SiO,     51.30 

Al,,63   1.95 

Undetermined 2.58 


The  greater  oxidation  of  iron  as  compared  with  manganese 
is  evident.  The  decrease  in  A12O3  also  is  apparent,  since  the 
refractory  lining  is  largely  silica  instead  of  largely  alumina  as 
in  fire  brick  structures.  The  silicon  entering,  the  slag  from  the 
metal  corresponds  to  12.1  per  cent  of  the  weight  of  the  slag. 
Therefore,  the  slag  consists  of  56.27  per  cent  compounds  de- 
rived from  the  oxidation  of  the  charge  and  43.73  per  cent  melted 

Comparing  the  iron  content  of  the  slag  with  the  iron  oxi- 
dized we  find  that  apparently  about  101  pounds  of  slag,  or 
5.05  per  cent  of  the  weight  of  the  metal  are  formed  per  ton 
charged  and  hence  by  calculation  44  pounds  of  refractories  or 
2.2  per  cent  are  melted  per  ton  of  metal  charged.  These  figures 
again  are  similar  in  order  of  magnitude  to  those  determined  by 
more  exhaustive  study  on  air  furnaces. 

Heat  Balance  Based  on  Assumed  Data 

The  heat  balance  of  an  open  hearth  can  be  calculated 
readily  from  a  knowledge  of  the  reactions  occurring.  Unfortu- 
nately we  have  not  a  complete  record  of  tests  involving  all  the 
factors  to  be  considered.  From  the  preceding  assumptions  and 
the  fact  that  the  average  natural  gas  consumption  of  the  furnace 
in  question  was  about  8200  cubic  feet  per  ton  when  regularly 
operated,  the  balance  in  Table  XIII  may  be  considered  as  an  ap- 
proximation, no  claim  to  precision  being  warranted  by  the  char- 
acter of  the  data. 

Expressing   results   in   per   cent   of   the  heat   value   of    fuel 


American   Malleable   Cast  Iron 

used  and  summarizing  a  little  further  the  data  may  be  expressed 
as  in  the  summary  in  Table  XIII. 

In  comparison   with  air   furnace   practice   it   will  be   noted 
that  a   general   increase   in   economy   is   shown,    10.22   per   cent 
of  the  heat  of  the  fuel  being  effective  instead  of  7.81  per  cent. 
The  waste  in  sensible  heat  of  flue  gas  and  the  loss  due  to  in- 
Table  XIII 

B.t.u.  B.t.u. 

Heat    value    of   fuel 8,514,000 

Heat  value  of  metal  oxidized 294,000 

Heat   formation    of   silicates    (estimated)     36,000 

Total     heat     input     , 8,844,000 

Latent  heat  of  fusion  and  sensible  heat  of  metal   879,000 

Sensible   heat   of    flue   gas    t 3.007,000 

Loss   due   to  uncomplete   combustion   of   C  to   CO   only....  545,000 

Sensible    heat    slag     51,000 

Latent    heat    fusion    slag    estimated    36,000 

Radiation  conduction  and  stand  by  losses    4,326,000 

Total    heat    output    8,844,000 

Summary    of   Pleat   Balance   of    Open-Hearth   Furnace 

.Per         Pei- 
cent         cent 

Heat  value  of  fuel    100.00 

Heat  reactions    in   bath 3.86 

Totals     103.86 

Heat   in   metal 10.22 

Heat   in    flue   gas 35.33 

Heat    in    slag 1.02 

Incomplete    combustion , 6.41 

Radiation    and    standby    losses    50.88 


complete  combustion  are  decreased  because,  being  gaseous  or 
liquid,  the  fuel  is  all  consumed  and  because  hydrogen  is  present. 
Since  the  furnace  constantly  is  kept  hot,  there  is  no  perceptible 
heat  loss  due  to  sensible  heat  of  furnace  wall.  However, 
there  is  a  large  loss  due  to  the  need  of  keeping  some  heat  on  the 
furnace  during,  idle  periods. 

This  loss,  increasing  with  the  idle  time,  makes  24-hour 
a  day  operation  highly  desirable.  With  such  operation  it  seems 
that  possibly  25  per  cent  of  the  present  fuel  could  be  saved. 
Radiation  and  conduction  losses  would  still  exist  but  stand  bv 

Cupola  and  Open  Hearth  Melting 187 

and  sensible  heat  losses  would  be  eliminated.  Under  such 
conditions  an  economy  of  about  14  per  cent  in  the  use  of  fuel 
might  be  reached  as  against  about  8  per  cent  in  air  furnace 
practice  in  24  hour  operation. 

Open-hearth  furnace  heats  range  in  size  from  14  to  20 
tons  or  more,  preferably  at- least  two  heats  a  day  being  made  on 
a  furnace.  Fuel  in  the  plant  in  question  is  natural  gas  or 
oil.  The  gas  consumption  varies  from  8200  to  9100  cubic  feet 
per  ton. 

Oil  fuel  runs  from  43  to  62  gallons  per  ton.  In  both  cases 
the  results  depend  on  whether  or  not  the  furnace  operates  con- 
tinuously or  intermittently  and  on  the  condition  of  the  furnace. 

For  heats  from  15  to  18  tons  in  size  about  5  to  ST/2  hours 
are  consumed  in  melting;  20-ton  heats  take  around  six  hours. 

The  efficiency  of  design  is  largely  dependent  on  the  checker 
arrangement'  with  its  corresponding  effect  on  the  utilization  of 
waste  heat.  Unlike  an  air  furnace,  the  open  hearth  requires 
rather  infrequent  but  very  extensive  repairs.  Furnace  bottoms 
and  banks  are  of  course  continuously  watched  and  patched  be- 
tween heats.  One  furnace  operated  two  years  and  two  months, 
making  1282  heats  with  no  repairs  except  cleaning  the  checkers 
and  changing  doors.  The  same  furnace  has  since  made  2051 
heats  with  one  cleaning  of  the  checkers,  a  new  roof,  front,  back 
and  bridgewalls,  an  unusual  record. 

On  the  other  hand,  another  furnace,  running  on  one  heat 
a  day  and  frequently  cooled  ran  only  200  heats  before  extensive 
repairs  were  required,  showing  the  extreme  destruction  from 
unequal  expansion  in  heating  and  cooling  of  the  brick. 

The  labor  to  operate  an  open  hearth  consists  of  either  three 
or  two  and  one  half  men  per  furnace.  Charging  is  not  included 
in  this  labor.  The  'work  of  charging  into  a  furnace  through 
doors  is  prohibitively  heavy  and  charging  machines  are  almost 
a  necessity. 

No  data  as  to  the  use  of  pulverized  coal  or  producer  gas 
are  available  for  malleable  melting,  although  both  of  these  fuels 
are  -used  in  steelmaking  with  great  success. 



THUS   far  in  the  discussion  of  malleable  foundry  practice 
the  various  methods  of  producing  molten  white  cast  iron 
have   been    considered.      The   next   step    is   converting   the 
hard  iron  casting  into  the  malleable  casting  of  commerce. 

Unfortunately  this  process  still  is  most  widely  known  as 
annealing  instead  of  the  better  terms,  heat  treating,  graphi- 
tizing,  or  converting.  It  is  the  intention  to  describe  mainly 
the  practical  execution  of  the  process  in  this  chapter. 

The  process  primarily  is  only  an  effect  of  time  and  tem- 
perature, and  not  a  chemical  one  in  the  sense  of  a  change 
of  composition.  Therefore  a  general  consideration  of  the 
subject  should  begin  with  the  viewpoint  of  the  general  meth- 
ods of  application  of  temperature  to  the  product,  leaving  for 
later  discussion  the  practical  limitations  of  temperature  and 
time  and  the  incidental  change  of  chemical  composition  in- 

The  practice  of  annealing  as  originally  developed  con- 
templated packing  the  castings  in  a  chemically  active  pack- 
ing material  in  cast  iron  containers  and  transferring  them 
into  an  oven  where  the  desired  heat  treatment  was  executed. 
This  method  of  operation  still  is  used  conveniently,  although 
it  is  now  thoroughly  recognized  that  the  use  of  packing  is 
by  no  means  an  essential  in  the  process.  In  addition  to  its 
control  over  the  chemical  changes  occurring  in  the  product 
by  oxidation,  the  packing  has  the  important  function  of  sup- 
porting the  casting  while  hot. 

Packing  Supports  Castings 

Commercial  annealing  contemplates  the  attainment  of 
maximum  temperatures  of  from  1500  to  1850  degrees  Fahr. 
and  the  maintenance  of  such  temperatures  for  days  at  a  time. 
Obviously  iron  at  this  temperature  will  be  fairly  soft  and  a 


American   Malleable   Cast   Iron 

casting  of  any  intricacy  would  be  irretrievably  ruined  by 
sagging  if  not  supported.  Except  in  such  special  cases  as 
may  arise  w'here  the  design  of  the  part  is  such  as  to  be  prac- 
tically self  supporting,  some  method  therefore  must  be 
adopted  for  preventing  the  distortion  of  the  casting  either 
under  its  own  weight  or  under  the  weight  of  the  castings  in 
the  pots  above  it. 

A  second  function  of  packing,  in  its  present  application 
is  to  hinder  rather  than  to  accelerate  oxidation.     If  a  casting 


Fig.     89. — Separator     plate     designed     to     eliminate 
with    annealing   pots 

use     of     packing 

be  exposed  directly  to  the  products  of  combustion  of  the  fuel 
at  these  high  temperatures  it  will  come  out  badly  scaled  and 
possibly  ruined  for  the  purpose  intended.  There  are  few 
better  means  of  protecting  the  casting  from  furnace  gases 
than  enclosing  it  in  a  fine  inert  packing. 

How  Castings  Are  Packed 

The  process  of  packing  is  carried  out  in  malleable  an- 
nealing as  follows.  First  a  bottom  which  is  practically  a 
heavy  cast  iron  bench  with  legs  4  or  6  inches  high  is  set  on 
the  floor.  On  this  is  set  a  pot  which  is  an  approximately 
rectangular  or  round  frame,  usually  about  12  inches  deep. 

Annealing   Practice  191 

The  size  and  form  of  pot  depends  largely  on  the  work 
handled  and  to  some  extent  on  the  whim  .of  the  annealer. 

Unusually  large  pots  fill  the  space  in  the  furnace  more 
completely  than  smaller  pots  but  heat  slowly  and  rather  un- 
evenly due  to  the  low  conductivity  of  the  packing  'material. 
Round  pots  do  not  distort  as  much  due  to  the  sagging  of 
the  contents  as  do  those  with  flat  sides.  However,  they  heat 
more  slowly  and  do  not  utilize  the  furnace  capacity  as  ef- 
ficiently as  the  latter.  Furthermore  in  most  places  the  pots 
are  handled  by  hand  so  that  too  great  weight  must  be 
avoided.  The  pots  must  be  about  1  inch  thick  to  have  a 
commercial  life  and  hence  extremely  large  pots  can  not  be 
made  as  deep  as  smaller  ones.  Also  when  large  they  are  not 
easily  stacked  very  high  and  therefore  a  waste  of  oven  ca- 
pacity may  result. 

The  writer  has  seen  rectangular  pots  as  large  as  30  x  36- 
inches  inside  used  where  the  character  of  the  castings  made 
this  size  unavoidable.  Round  pots  frequently  are  24  to  30 
inches  inside  diameter.  Rectangular  pots  running  from 
about  14  x  18  inches  to  16  x  24  inches  inside  are  common. 

AY  here  the  work  is  of  such  character  as  to  stack  solidly 
together,  a  pot  of  the  smaller  size  or  only  a  little  larger  will 
give  a  stack  as  heavy  as  can  be  readily  moved  or  uniformly 
heated.  In  thin,  sprawly  work  larger  sizes  may  be  unavoid- 
able. The  pots  are  made  of  white  cast  iron  either  like  that 
in  the  castings  or  of  a  cheap  cupola  iron  high  in  sulphur 
and  low  in  manganese  which  will  not  graphitize. 

Method  of  Packing  Pots 

After  the  pot  has  been  placed  upon  the  stool,  the  first 
step  is  to  put  in  a  layer  of  packing  from  one  to  three  inches 
thick.  On  this  are  shoveled  or  packed  sufficient  castings  to 
nearly  fill  the  pot.  Small  castings,  for  example  link  belt 
parts,  are  shoveled  in.  Large  castings  usually  are  set  in  reg- 
ularly to  conserve  space,  care  being  -taken  to  fill  the  spaces 
remaining  inside  or  between  large  castings  with  smaller  ones 
as  far  as  practicable.  As  much  packing  is  shoveled  in  from 
time  to  time  as  can  be  made  to  run  down  into  the  spaces 

192  American  Malleable   Cast  Iron 

still  remaining.  Extremely  complicated  work  must  be  placet! 
carefully  so  that  it  may  be  perfectly  supported  at  all 
points.  This  sometimes  necessitates  the  use  of  special  plates 
and  other  supporting  devices  designed  particularly  for  the 
part  in  question. 

Factors  Affecting  Heights  of  Stack 

When  the  first  pot  is  nearly  full  a  second  one  is  set  on 
it  and  the  packing  continued  as  before.  The  building  up 
is  continued  until  the  stack  of  pots  is  from  3^  to  6  or  7  feet 
high  above  the  top  of  the  stool  depending  on  the  height  of 
furnace  and  the  ideas  of  the  annealer.  Care  is  taken  that 
the  top  pot  be  finished  Avith  several  inches  of  packing  into 
which  no  castings  project  and  usually  the  top  is  covered  with 
a  plate  or  with  fire  clay,  or  both.  A  reasonable  height  must 
be  attained  to  secure  economy,  of  space.  On  the  other  hand, 
stacks  of  excessive  height  are  not  only  difficult  to  heat  uni- 
formly but  are  subject  to  careless  packing  since  the  packet- 
must  stand  on  a  stool  and  pack  in  an  inconvenient  position. 
High  stacks  also  are  easily  upset  in  handling.  The  writer 
favors  a  stack  four  pots  high  where  the  individual  pots  are 
12  to  15  inches  deep,  thus  making  a  maximum  height  of 
stack  of  60  inches  above  the  top  of  the  stool. 

In  any  event,  after  the  packing  is  complete  and  before 
the  cover  is  put  on,  the  stack  of  pots  is  rapped  with  a  heavy 
hammer  or  otherwise  jarred  to  settle  the  packing  solidly.  It 
is  easy  to  leave  20  to  30  per  cent  of  voids  due  to  careless 
packing.  This  not  only  reduces  the  capacity  but  permits  the 
ingress  of  furnace  gases  and  also  lets  the  charge  settle,  usu- 
ally unevenly.  The  result  is  badly  warped  castings,  scaly  iron 
.and  possibly  some  completely  burned  castings  in  the  top 
pots  where  the  packing  has  sunk  away. 

The  life  of  an  annealing  pot  depends  somewhat  upon 
its  composition,  but  more  largely  upon  the  furnace  atmo- 
sphere to  which  it  is  exposed.  Pots  which  crack  from  in- 
ternal stresses  do  so  in  the  first  or  at  least  in  an  early  ex- 
posure in  the  furnace.  Thereafter  failure  is  by  oxidation  of 
the  surface,  which  depends  on  the  thickness  of  the  pot.  tern- 

Annealing   Practice  193 

perature  of  the  furnace,  time  the  pot  is  in  the  furnace,  and 
combustion  conditions.  A  life  of  from  only  10  to  12  passes 
is  frequent,  but  the  average  probably  lies  between  15  and 
25  passes.  Under  favorable  conditions  a  pot  m'ay  survive 
from  30  to  50  trips  through  the  furnace. 

Pots  are  made  either  of  the  same  metal  used  for  castings 
or  of  white  cast  iron  from  a  cupola  operated  for  that  pur- 
pose. In  the  latter  case  the  mix  is  usually  such  as  to  pro- 
duce a  sulphur-manganese  ratio  which  nearly  prevents 
graphitization.  This  is  an  advantage  as  reducing  the  growth 
of  pots  in  use. 

The  heating  of  an  annealing  furnace  is  invariably  from 
the  top  down.  This  causes  the  top  of  a  stack  of  pots  to  heat 
first.  It  is  customary  to  counteract  this  tendency  by  pack- 
ing the  light  work  in  the  bottom  and  the  heavy  work  in  the 
top  so  that  the  greatest  thermal  capacity  is  nearest  the  source 
of  heat. 

The  packing  of  castings  is  a  fairly  expensive  operation 
involving  considerable  skill  which  if  slighted  is  productive  of 
bad  work  and  loss  of  castings. 

Various  schemes  have  been  suggested  for  working  in 
empty  pots  to  avoid  packing.  These  take1  the  general  form 
of  a  set  of  plates  between  the  several  pots  so  that  the  ma- 
trial  in  the  bottom  pot  does  not  have  to  carry  the  entire 
weight  of  metal  above.  Such  methods  were  employed  suc- 
cessfully for  many  years  but  require  careful  exclusion  of  air. 

J.  H,  Fryer  recently  introduced  a  design  of  separator 
plate  as  shown  in  Fig.  89  which  by  its  flanged  construction 
permits  the  making  of  a  good  clay  seal.  While  particularly 
important  in  pots  where  packing  is  not  used,  'this  sealing 
also  is  required  in  the  usual  practice. 

The  pots  prepared  by  any  of  these  methods  are  intro- 
duced into  annealing  ovens,  which  are  merely  fire  brick 
chambers  capable  of  being  heated  to  the  desired  tempera- 
ture. Some  idea  of  the  dimensions  of  these  ovens  has  already 
been  given  in  ithe  general  description  of  a  malleable  foundry. 
Ovens  may  hold  from  25  to  100  stacks  of  pots,  neither  ex- 
treme being  common.  Nearly  all  ovens  are  deeper  than  they 


American   Malleable   Cast   Iron 

Annealing   Practice  195 

are  wide,  and  the  flame  usually  travels  from  back  to  front. 
A  number  of  exceptions  exist  more  particularly  in  pulverized 
fuel  or  oil-fired  furnaces.  The  older  ovens,  and  particularly 
the  smaller  units  frequently  were  builit  in  sets  of  two  to 
eight  ovens.  In  this  way  the  loss  of  heat  through  the  side 
walls  and  the  waste  of  floor  space  was  minimized.  Heavy 
walls  about  32  inches  thick  sometimes  were  employed  to 
serve  as  heat  insulators.  More  recently,  with  the  advent 
of  various  types  of  heat  insulating  brick  the  actual  wall 
thickness  has  been  reduced. 

Fig.    91. — Charging    trucks    facilitate    the    handling    of    pots    to    and 
from  the  annealing  furnaces 

Many  designers  laid  great  stress  on  heating  the  anneal- 
ing furnace  floors  by  elaborate  systems  of  checkers  or  flues 
through  which  the  waste  heat  of  the  furnace  passed.  Other 
designers  preferred  to  use  only  the  necessary  flues  to  carry 
off  the  flame  from  the  furnace. 

Large   Ovens  More  Economical 

Large  ovens  are  economical  of  fuel  as  they  present  rela- 
tively little  wall  surface  per  unit  of  metal  content.  However, 
they  usually  are  harder  to  heat  uniformly,  and  therefore  re- 
quire greater  skill  in  design.  A  number  of  engineers  feel 

196  American  Malleable   Cast   Iron 

that  wide  arches  are  expensive  to  maintain.  The  relative 
importance  of  these  factors  in  the  mind  of  the  designer  usu- 
ally influences  the  construction  chosen  in  any  given  case. 
It  is  not  likely  that  any  wide  difference  in  performance  is 
to  be  expected  from  the  possible  variations  in  furnace  di- 
mensions. Economy  usually  dictates  the  use  of  a  local  coal 
for  annealing  fuel.  The  firebox  design  generally  is  extremely 
simple,  consisting  merely  of  an  area  fenced  off  in  a  back 
corner  of  the  furnace  by  two  walls  a  little  higher  than  the 
stack  of  pots  used.  The  grates,  within  this  area,  are  fired 
through  the  rear  Avail.  Occasionally,  instead  of  providing  an 
inside  firebox,  the  firebox  is  built  outside  the  furnace  against 
the  rear  wall  and  communicates  with  the  furnace  chamber 
through  a  fire  'hole,  which  is  like  a  window  through  a  wall. 

Various  stoking  devices,  including  automatic  coal  feeds', 
shaking  grates,  etc.,  have  been  used,  but  none  of  these  seems 
to  have  commended  itself  sufficiently  to  gain  a  firm  foothold 
in  the  industry.  Possibly  the  explanation  is  that  the  firing 
operation  in '  annealing  does  not  require  as  careful  control 
as  in  melting. 

It  is  desirable  both  in  the  interest  of  economy  and  in 
order  to  avoid  rapid  burning  of  the  annealing  pots  that  an 
excess  of  air  be  prevented  from  entering  the  furnace.  How- 
ever with  well  packed  pots  the  process  will  be  operative, 
though  uneconomical,  if  this  precaution  is  neglected.  Thus 
there  has  been  little  incentive  to  control  annealing  firing  as 
closely  as  the  melting  operation  where  the  making  of  good 
iron  is  impossible  with  poorly  controlled  fires. 

Many  producers  of  whom  B.  J.  Walker  is  considered  the 
pioneer,  have  experimented  with  pulverized  fuel  in  anneal- 
ing and  a  good  measure  of  success  has  attended  their  efforts. 
The  arrangements  employed  are  of  the  same  character  as  in 
air  furnace  firing,  although  the  problem  is  slightly  les:;> 

The  standard  design  of  annealing  oven  contemplates  the 
introduction  of  the  pots  at  the  front  of  the  furnace.  The 
opening  is  closed  by  doors,  usually  made  in  sections  which 
are  equivalent  to  a  front  wall. 

Annealing   Practice 


At  an  early  date  attempts  were  made  to  render  the  pro- 
cess approximately  continuous.  Seth  Boyden  built  a  "shov- 
ing" furnace  of  which  G.  H.  Kings  land  of  the  Wilmington 
Malleable  Iron  Works  writes  as  follows : 

"The  furnace  was  torn  down  under  my  direction.  The 
pots  were  12  inches  high  and  10  inches  wide  each  way,  with 

Fig.    92. — The     interior    of     the    powdered     coal    mill    of    a    modern 
malleable  plant.     The  horizontal  cylinder  at  the  left  is  the  dryer 

a  bottom  just  like  a  box  without  a  cover.  These  were  placed 
on  rollers,  pots  being  pushed  in  at  one  end  and  shoved  out 
at  the  other.  I  believe  the  furnace  held  30  of  these  boxes, 
five  wide  and  six  deep.  One  row  of  five  was  shoved  out  each 
working  day  and  a  row  of  five  pushed  in.  The  furnace  was 
about  2  feet  high  at  the  crown  of  the  arch,  with  flues  under 


American   Malleable   Cast   Iron 

3     O 

M-      ,0 

<u    ^ 

•5    v 

C     rt 

Annealing   Practice  199 

the  floor  and  in  the  side  walls  running  to  a  stack  about  25 
feet  away  through  a  vitrified  pipe.  The  Barlow  people  later 
charged  the  entire  furnace  at  one  time  instead  of  at  the  rate 
of  five  pots  daily." 

Limitations  of  Removable  Roof 

In  order  to  permit  the  loading  of  annealing  furnaces  by 
cranes  the  design  is  sometimes  modified  by  forming  the  roof 
of  removable  arch-shaped  sections,  like  the  bungs  in  an  air 
furnace.  In  this  case  no  doors  are  required  and  the  furnace 
is  usually  submerged  in  the  ground  almost  to  the  spring  line 
of  the  arch. 

The  heat  insulation  of  the  side  walls  in  such  furnaces 
is  unusually  good  but  heat  losses  'through  the  roof  are  large 
since  the  limits  of  weight  prevent  the  use  of  a  roof  of  suffi- 
cient thickness.  Moreover,  the  construction  involves  a  great 
number  of  joints  in  the  roof  which  are  difficult  to  seal. 
The  wid'th  of  furnaces  of  this  type  is  restricted 
because  of  the  prohibitive  weight  of  long  roof  sections. 
Therefore  the  design  is  along  the  lines  of  a  relatively  long 
and  narrow  unit,  as  compared  with  the  nearly  square  floor 
plan  of  the  ordinary  furnace. 

It  is  important  that  the  furnace  structure  be  protected 
from  the  effect  of  moisture  if  water  is  present  in  the  soil 
in  which  the  furnace  is  set.  A  story  regarding  a  battery  of 
furnaces  built  near  a  river  subject  to  spring  floods  is  well 
known  in  the  mallealble  industry.  To  the  astonishment  of 
their  builder,  these  furnaces  became  miniature  lakes  when 
the  back  water  from  the  first  flood  rose  to  a  level  higher 
than  the  furnace  floor. 

The  practice  thus  far  described  involves  the  use  of  pots 
either  with  or  without  packing.  Since  pots'  and  packing  are 
expensive,  efforts  have  been  made  to  dispense  with  con- 
tainers, muffle  annealing  being  the  outgrowth  of  these  at- 

Muffle-type  Furnaces 

Muffle  furnaces — not  "muffled"  as  frequently  pro- 
nounced and  even  spelled — are  constructed  so  that  the  flame 
from  the  fire  box  or  burner  does  not  come  in  contact  with 


American   Malleable   Cast   Iron 

Fig.    94. — Diagram    showing    the    distribution    of    heat    in    a    contin- 
uous-type annealing   furnace 

Fig.      95.  —  Interior      of      continuous-type      annealing      furnace      looking 
toward  the  entrance  end 

Annealing   Practice  201 

the  castings  to  be  annealed.  In  their  general  design  muffle 
furnaces  represent  the  usual  oven  with  the  addition  of  a 
separate  interior  chamber  or  chambers.  As  usual,  the  flame 
enters  the  oven  but  instead  of  filling  the  entire  space  it 
merely  passes  through  the  spaces  between  the  interior  cham- 
bers or  muffles  and  the  walls,  floor  and  roof.  The 
muffles  are  built  as  thin  as  possible  usually  4^  inches  thick, 

Fig.     96. — Single     section     of     combustion     chamber     of     continuous-type 

annealing  furnace 

in  the  interest  of  low  thermal  capacity  and  good  heat  con- 
ductivity. The  castings  to  be  annealed,  which  must  be  of  a 
character  not  to  distort  easily  when  hot,  are  stacked  in  the 
muffles,  the  front  of  the  muffles  bricked  up  and  the  oven 
proper  closed  with  the  usual  doors.  The  heat  treatment  is 
identical  with  that  in  the  ordinary  annealing  furnace. 

At  the  conclusion  of  the  treatment  the  castings  are  re- 
moved by  hand ;  consequently  the  furnace  cannot  be  "pulled" 
until  the  contents  are  well  cooled.  Therefore  the  output 
of  the  furnace  is  decreased  by  the  time  taken  for  cooling  to 


American   Malleable   Cast   Iron 


£    o 

•^     b 

*oj    o 

(L)       O 


rt    u 

X!      C 

§  s 


Annealing   Practice  203 

this  temperature  as  compared  with  the  time  to  cool  suffi- 
ciently to  pull  pots  mechanically.  The  thermal  efficiency 
also  is  decreased  since  the  heat  must  be  transmitted  to  the 
castings  through  the  intervening  brick  wall.  On  the  other 
hand,  the  cost  of  pots  and  packing  and  the  cost  for  heating 
pots  and  packing  are  saved. 

In  view  of  the  fact  that  the  efficiency  of  annealing  fur- 
naces is  largely  determined  by  the  'heat  insulation  of  the 
walls  and  roofs  and  is  consequently  widely  different  in  dif- 
ferent plants,  it  is  difficult  to  speak  with  assurance  as  to  the 
relative  economy  of  muffle  and  pot  furnaces.  The  general 
impression  toward  muffle-type  furnaces  seems  to  be  favor- 
able. Reliable  tests  can  only  be  made  by  weighing  coal 
and  iron  on  a  series  of  runs  in  each  of  two  furnaces  of 
identical  exterior  construction,  one  loaded  with  pots  the 
other  having  a  muffle  built  within  it. 

The  coal  consumption  for  annealing  varies  greatly  in 
commercial  practice.  .Plants  of  good  reputation  burn  around 
1000  pounds  of  coal  per  ton  of  iron  annealed,  although  with 
well-built  furnaces  and  particularly  with  pulverized  fuel 
much  better  records  should  be  obtained.  A  quantitative 
idea  of  the  heat  values  involved  may  be  obtained  from  Table 
XIV,  which  is  based  on  the  theoretical  heat  requirements  of 
the  various  reactions  involved. 

These  figures  are  for  the  minimum  possible  use  of  fuel, 
making  no  allowance  for  incomplete  or  other  imperfect  com- 
bustion conditions,  radiation  from  furnace  walls,  heat  car- 
ried out  by  convection  currents  of  cold  air  when  the  fur- 
nace is  supposed  to  be  cooling  slowly,  conduction  of  heat 
into  the  ground,  etc.  All  of  these  losses  exist  and  are  of 
large  magnitude.  The  aggregate  of  all  losses  is  what  makes 
up  the  difference  between  the  theoretical  coal  consumption 
of  274  pounds  per  ton  and  the  actual  commercial  figures 
of  600  pounds  to  1000  pounds  per  ton. 

Another  way  of  approximating  the  radiation  and  similar 
losses  is  by  considering  the  fact  that  an  annealing  furnace 
of  ordinary  construction  will  cool  from  1500  to  1300  degrees 


American  Malleable   Cast  Iron 

Table  XIV 


Available  Heat  of  Fuel 

B.t.u.      B.t.u. 

Heat  value  per  pound  coal 12,500 

Flue  gas  from  1  pound  coal  theoretical  combustion  conditions: 
3.8   pound    COa 

0.4  pound  H2O 

13.2  pound  N 

17.4  Total 
Total    sensible   and    latent    heat    in    flue    gas    from    1 

pound  coal  at  1100  degrees  above  atmosphere 5,000 

Total  heat  in  cinders  from  1  pound  coal,  sensible  heat 

and  heat  of  combustion  of  unburned  fuel    160 

Maximum  available  heat  per  pound  of  coal    (12,500- 

5,160)    7,340 

Total     12,500          12,500 

Thermal  Capacity   Oven  and   Charge 

Total  heat  1  ton  castings  at  1650  degrees  above  atmosphere  389,400 
Total  heat  in  \l/2  tons  pots  and  1125  pounds  packing  at 

above  temperature  955,350 

Total  heat  wall,  floor  and  roof  3900  pounds,  brick  per  ton 

charge  raised  average  of  1200  degrees. Fahr 624,000 

Total  sensible  heat  furnace  contents  per   1   ton  casting 

(of  this    19.8  per   cent  only   is   in   castings) 1,968,750 

Heat  from  Chemical  Reactions 

Heat  from  decarburi.zation  1  ton  castings  l/2  per  cent  or 

10  pounds  carbon  burned  to  CO2 142,200 

Heat  absorbed  by  reaction  (10,  pounds  carbon)  6  FeO  +  5C  = 

CQ2  +  4  CO  +  6  Fe  , 136,360 

Heat  evolved  by  decarburizing  per  ton  of  castings 5,840* 

Heat  absorbed  by  graphitization  of  2  per  cent  carbon  per  ton 

castings.  Reaction  Fe3C  =  3  Fe  -j-  C  53,640 

Heat  required  to  maintain  chemical  reaction  per  1  ton  of 

castings      47,800 

Resume  Based  on  1  Ton  Product 

Sensible    heat    castings     389,400 

Heat  of  reaction    47,800 

Useful   heat 437,200 

Sensible  heat  furnaces,  pots  and  packing   1,579,350 

Total   heat    2,016,550 

Total  heat  required  in  oven  at  7340  B.t.u.  per  pound  of  coal  =  274 
pounds  coal  per   ton. 

*Exact   decarburizing    reactions    unknown.     Assumption    made    on 
basis   of  known   composition  of  resulting  gases. 

Annealing   Practice  205 

Fahr.  in  from  25  to  50  hours,  depending  mainly  on  the  size 
of  furnace  and  the  heat  insulating  ability  of  the  walls. 

The  area  of  walls  and  roof  of  an  annealing  furnace  totals 
about  35  to  40  square  feet  per  ton  of  capacity.  With  the 
foregoing  figures  it  can  be  calculated  that  about  239,000 
B.t.u.  per  ton  of  castings  must  be  radiated  to  cool  the  furnace 
200  degrees.  This  at  the  rate  in  round  numbers  of  6800 
B.t.u.  per  square  foot  of  oven  surface  (average  furnace  tem- 
perature 1400  degrees  Fahr.)  which  in  turn  is  at  a  rate  of 
between  136  and  272  B.t.u.  per  square  foot  per  hour. 

Table   XV 


Total  heat  in  900  pounds  coal  at  12,500  B.t.u.  =  11,250,000  B.t.u.  per  ton 
of   castings  ~   100   per    cent 

B.t.u.         Per  cent 

Heat  for  chemical  reaction  in  1  ton  of  castings   .  .         47,800  0.52 

Sensible   heat   in    1    ton   of  castings    389,400  3.46 

Sensible  heat  in  pots  and  packing 955,350  8.48 

Sensible    heat   in    furnace    structure    624,000  5.54  . 

Radiation  and   conduction,    furnace   structure    ....       750,000  6.66 
Sensible    and    latent    heat     flue     gas     (theoretical 

combustion)     4,500.000  40.00 

Heat  loss  in  cinders  and  air  leakage    .  .  .  .  = 144,000  1.24 

Sensible    heat,   excess    air.    error   and    unaccounted 

for     (excess    temperature,    etc.) 3,839.450  34.10 

Total   ' 11,250,000       100.00 

Assuming  that  1400  degrees  is  the  approximate  mean 
inside  temperature  while  the  furnaces  is  under  fire,  the  oven 
loses  heat  by  radiation  and  conduction  at  the  rate  of  be- 
tween 5000  and.  10,000  B.t.u.  per  hour  per  ton  of  contents. 

Therefore  with  poor  insulation  the  heat  lost  per  ton 
from  these  sources  will  be  10,000  B.t.u.  per  hour  that  the 
furnace  is  fired,  or  80,000  to  1,200,000  B.t.u.  which  figure  may 
be  halved  by  good  insulation.  This  is  equivalent  to  from 
55  to  165  pounds  of  coal  per  ton,  an  amount  insufficient  to 
account  for  all  the  coal  frequently  used.  The  remaining 
losses  presumably  are  due  to  intake  of  cold  air,  excess  air 
for  complete  combustion,  excess  temperature  of  outgoing 
air,  etc.,  and  other  similar  losses  to  be  determined  only  as 
the  result  of  experimental  investigation. 

206  American   Malleable   Cast  Iron 

An  idea  of  the  heat  balance  may  be  obtained  from  Table 
XV,  which  is  based  on  an  assumed  coal  consumption  of  900 
pounds  per  ton  of  castings  with  only  fair  insulating  and 
combustion  conditions.  The  last  item  of  the  table  is  equiva- 
lent to  a  little  less  than  50  per  cent  excess  air. 

It  will  be  noted  from  the  table  that  only  about  J^  per 
cent  of  the  heat  of  the  fuel  is  expended  usefully  in  the  chemi- 
cal- changes,  which  are  the  purpose  of  the  annealing  opera- 
tion, 0.01  per  cent  in  producing  the  accompanying  change  in 
volume  and  only  3j/2  per  cent  additional  in  heating  the  cast- 
ings themselves  to  the  requisite  temperature  for  the  reaction 
to  take  place. 

Obviously  the  thermal  efficiency  of  the  process  is  ex- 
tremely low,  due  to  the  great  heat  capacity  of  the  oven  and 
its  contents  and  to  the  great  amount  of  heat  which  is  car- 
ried out  by  the  avoidably  large  mass  of  gas  at  fairly  high 
temperature.  If  the  alternate  heating  and  cooling  of  the 
furnace  structure  could  be  avoided,  if  the  furnace  gases  could 
leave  the  chamber  at  temperatures  lower  than  that  of  the 
pots  at  their  maximum  and  if  the  sensible  heat  of  the  pots 
after  anneal  could  be  transmitted  to  other  pots  just  heating, 
greater  economy  could  be  effected.  Attempts  to  do  this  have 
been  shaped  in  various  continuous  annealing  processes  using 
tunnel-shaped  kilns. 

The  Dressier-type  kiln  originally  designed  for  use  in  an- 
nealing sheets  and  also  for  use  in  the  ceramic  industries 
is  just  entering  the  field.  Only  3  of  these  have  so  far  been 
constructed  .and,  owing  to  business  conditions  only  one  has 
operated  for  a  considerable  continuous  period  of  time.  The 
principle  of  operation  is  that  the  heat  treatment  is  accom- 
plished by  passing  the  furnace  charge,  on  cars,  slowly  through 
a  long  tunnel  of  relatively  small  cross  section.  The  tunnels 
are  about  300  feet  long  and  the  cars  of  castings  or  pots  pass 
through  in-  the  time  required  for  one  annealing  cycle. 

Any  given  part  of  the  tunnel  remains  constantly  at  one 
temperature.  The  temperature  varies  along  the  length  of 
the  furnace  to  correspond  to  the  changes  in  temperature 

Annealing   Practice  207 

which  may  be  desired  as  the  castings  pass  through  the  op- 
eration. Special  forms  of  heating  units  have  been  developed 
using  oil,  gas  or  pulverized  coal  which  are  conducive  to 
efficient  circulation  of  the  hot  furnace  atmosphere  without 
necessarily  contaminating  it  by  admitting  the  flame  itself. 

Heaters  Installed  for  High  Temperatures 

The  heaters  are  installed  where  the  highest  temperatures 
are  required  and  the  products  of  combustion,  leaving  them 
at  a  temperature  low  enough  to  make  the  further  transfer 
of  heat  to  pots  at  their  highest  temperature  impossible,  pass 
on  and  are  further  used  to  begin  the  heating  of  pots  just  en- 
tering the  furnace  and  to  preheat  the  air  for  combustion. 

Further  details  of  construction  involve  the  use  pi  air 
locks  to  permit  the  work  to  enter  and  leave  the  kiln 
without  admitting  air,  the  mechanical  means  of  moving  cars 
through  the  furnace,  etc.  In  the  absence  of  any  operating 
data  on  such  kilns  in  malleable  practice  the  effect  on  fuel 
saving  can  only  be  surmised.  The  principal  sources  of  fuel 
economy  which  may  be  expected  in  a  continuously  operated 
kiln  are  the  following: 

First,  the  fact  that  the  furnace  structure  is  neither 
heated  nor  cooled  results  in  a  saving  on  the  basis  of  our 
previous  figures  of  624,000  B.t.u.  per  net  ton.  Second,  the 
fact  that  since  the  flue  gases  and  also  the  product  being 
annealed  impart  much  of  their  heat  to  the  incoming  material, 
the  loss  in  sensible  heat  of  flue  gases  and  of  pot  packing  and 
so  on  should  be  considerably  reduced.  Third,  the  furnaces  now 
in  use  being  oil  or  gas  fired,  should  permit  of  more  economical 
use  of  fuel  than  can  be  had  in  furnaces  fired  with  coal. 
Fourth,  it  should  be  possible  to  reduce  air  leakage  in  a  kiln 
of  this  type  far  below  what  could  be  done  in  the  case  of  a 
furnace  through  which  the  products  of  combustion  are  forced 
to  pass. 

Offsetting  these  economies  the  long  slender  furnace  pre- 
sents a  somewhat  greater  surface  per  ton  of  content  so  that 
radiation  losses  would  increase  considering  an  equal  degree 
of  heat  insulation  in  the  tunnel  furnace  and  in  an  oven.  In 

208 American  Malleable  Cast  Iron 

practice  this  loss  is  largely  counteracted  by  efficient  heat  in- 
sulation on  the  walls  and  roof  of  the  structure. 

On  the  basis  of  entirely  arbitrary  assumptions  as  to  exit 
temperatures,  flue  gas  composition,  etc.,  the  writer  has  calcu- 
lated that  it  might  be  possible  to  anneal  a  ton  of  castings  in  a 
kiln  of  this  type  with  the  expenditure  of  about  2,100,000  B.t.u. 
It  must  be  clearly  understood  that  these  figures  are  speculative 
only,  and  in  no  sense  founded  upon  experimental  results. 

At  the  time  this  is  written  only  one  furnace  of  this  type 
has  been  operated  sufficiently  long  to  be  considered  beyond  the 
experimental  stage.  The  best  information  at  the  author's  dis- 
posal is  that  in  the  furnace  in  question  about  four  million 
B.t.u. 's  were  required  for  annealing  a  ton  of  product. 

As  in  the  case  of  electric  melting  furnace  equipment  it  must 
be  remembered  that  the  entire  plant  layout  must  be  adapted  to 
the  use  of  the  continuous  kiln  and  suitable  provisions  be  made 
for  the  transportation  of  trucks  and  the  mechanical  handling 
of  material  in  connection  therewith.  Also  as  in  the  case  of  the 
electric  furnace  a  very  considerable  first  cost  is  involved  as  com- 
pared with  the  simpler  units.  Again  as  in  the  case  of  the  elec- 
tric melting  operation  one  of  the  hoped  for  advantages  from 
the  use  of  the  more  elaborate  method  is  a  better  control  of  the 
product,  in  this  case  arising  from  the  greater  uniformity  of 
the  heat  cycle  to  be  expected  in  a  tunnel  kiln  operation  as  com- 
pared with  the  operation  of  a  furnace  which  has  temperatures 
varying  widely,  not  only  from  time  to  time,  but  also  from  place 
to  place  in  the  furnace.  Touceda  has  designed  annealing  fur- 
naces of  the  usual  form  in  which  attempts  are  made  to  carry 
the  elimination  of  heat  Josses  as  far  as  practicable.  He  has 
also  suggested  a  furnace  heated  by  fuel  in  which  the  tempera- 
ture Once  reached  would  be  maintained  electrically  by  nearly  au- 
tomatic means.  Such  a  furnace  if  practicable  would  be  very 
interesting.  At  least  one  concern  is  attempting  to  introduce 
an  electrically  heated  furnace.  This,  however,  is  decidedly  in 
the  experimental  stage.  So  much  for  the  practical  execution 
of  the  annealing  operation. 

Controlling  Annealing  Temperatures 

In  any  annealing  operation  pyrometric  control  will  be  required. 
Thermocouples  are  somewhat  frequently  introduced  in  nichrome  or 

Annealing   Practice  209 

ceramic  tubes  through  the  furnace  wall  or  roof.  The  practice 
has  the  advantage  of  a  quick  response  to  changes  of  firing  con- 
ditions and  is  the  only  one  possible  in  the  continuous  furnace. 
However,  it  does  not  give  any  data  as  to  the  temperature  of 
the  metal  itself  and  accordingly  it  is  advantageous  to  have  one 
or  more  couples  actually  within  the  pot.  The  interior  of  a 
good  sized  pot  'may  lag  15  or  20  hours  behind  the  furnace 
temperature.  The  lag  is  less  the  more  solidly  the  pot  is  filled 
with  iron  and  more  the  greater  the  per  cent  of  packing.  These 
figures  apply  when  the  furnace  temperature  is  known  and  uni- 
form. If  the  space  into  which  the  couple  penetrates  is  filled 
with  flame  then  the  flame  temperatures,  varying  as  they  may 
several  hundred  degrees  in  a  quarter  of  an  hour  or  less,  are 
absolutely  meaningless.  Theoretically  it  may  be  possible  to 
mount  a  couple  in  a  protection  having  the  same  temperature 
lag  as  an  average  pot. 

Many  satisfactory  pyrometric  equipments  are  on  the  mar- 
ket. Provision  for  automatic  recording  is  virtually  essential. 
The  writer's  preference  is  for  potentiometer  recorders.  He  fur- 
ther prefers  a  tape  record  to  a  disk  record.  In  large  plants 
multiple  point  recorders  are  convenient.  Noble  element  couples 
seem  commercially  undesirable  at  the  temperatures  involved,  both 
on  account  of  expense  and  the  low  electromotive  force.  In 
oxidizing  atmospheres,  couples  of  the  chromel  type  have  a  good 
life  but  neither  these  nor  platinum  will  survive  reducing  condi- 
tions. Iron-constantan  is  perhaps  most  satisfactory  under  those 

For  data  on  the  construction,  operation,  and  characteristics 
of  various  types  of  pyrometric  equipment  reference  is  suggested 
to  Technologic  Paper  170  of  the  United  States  bureau  of  stand- 
ards, "Pyrometric  Practice"  by  Foote,  Fairchild  &  Harrison. 

A  very  brief  exposition  of  principles  must  here  suffice. 

Any  thermocouple  sets  up  at  its  terminals  a  difference  of 
potential,  or  mill i voltage,  depending  upon  the  difference  in  tem- 
perature existing  at  the  junction  of  the  two  dissimilar  wires  and 
the  temperature  where  these  wires  are  joined  to  the  copper  of 
the  instrument  or  distributing  system.  To  know  the  tempera- 
ture of  the  hot  end  we  must  know  that  of  the  cold  end.  We 

210  American   Malleable   Cast  Iron 

may  read  this  with  a  thermometer  or  else  keep  it  constant  either 
by  burying  the  cold  end  in  the  ground,  circulating  around  it 
water  at  constant  temperature  or  introducing  it  into  a  ther- 
mostat kept  at  a  controlled  temperature  above  that  of  the  room 
by  electric  heaters  automatically  switched  on  and  off  to  main- 
tain a  fixed  temperature.  Boiling  water,  kept  supplied  to  re- 
place evaporation  may  be  used. 

There  are.  also  electric  devices  for  compensating  for  "cold 
end  temperature." 

The  thermocouple  electromotive  force  is  measured  by  a 
millivoltmeter  which  however  actually  measures  the  current 
set  up  by  the  electromotive  force  through  the  assured  constant  re- 
sistance of  the  instrument  and  external  circuit.  Since  current 
is  the  quotient  of  electromotive  force  divided  by  resistance  the 
readings  may  be  affected  just  as  'much  by  changes  of  resistance 
as  by  changes  of  electromotive  force.  Such  changes  are  coun- 
teracted by  making  the  resistance  of  the  instrument  high  as 
related  to  that  of  the  thermocouple  and  leads.  Accidental  changes 
of  resistance  external  to  the  apparatus  may  be  small  or  even 
negligible  fractions  of  the  total.  Such  high  resistance  instru- 
ments are  difficult  to  make  rugged.  Another  course  is  to  use 
low  resistance  instruments  and  take  pains  to  keep  the  total  re- 
sistance constant.  This  is  possible  but  troublesome.  All  indicat- 
ing instruments  depend  for  their  accuracy  on  ,come  torsion  mem- 
ber, springs  or  suspension  exactly  retaining  its  elastic  .prop- 
erties unaltered. 

The  only  available  means  for  directly  measuring  an  electro- 
motive force  is  to  oppose  it  to  another  variable  and  constantly 
known  potential  using  a  galvanometer  only  to  indicate,  by  the 
absence  of  any  current  when  the  t\vo  are  exactly  equal.  The 
apparatus  for  doing  this  is  called'  a  potentiometer.  Its  use  is 
usually  slightly  less  convenient  than  that  of  a  millivoltmeter 
but  avoids  all  errors  except  those  due  to  variations  in  tempera- 
ture of  the  cold  ends.  This  can  also  be  electrically  compen- 
sated. The  potentiometer  also  can  be  built  with  a  more  open 
scale  than  a  millivoltmeter  nor  need  the  scale  begin  at  zero,  so 
that  the  scale  length  available  can  be  used  for  only  that  range 

Annealing   Practice  211 

of  temperature  of  interest  in  the  process,  say  1000  degrees  to 
2000  degrees  "Fahr.  Either  type  of  apparatus  can  be  made  au- 
tographic. Although  this  is  slightly  more  complex  for  the  poten- 
tiometer type  this  system  has  the  advantage  that  the  motion  of 
the  pointer  is  rectilinear  and  not  a  circular  arc  as  in  the  gal- 
vanometer type  instruments. 



A  THOUGH    the    general    principles    of    graphitization   and 
decarburization  as  applied  to  annealing  and  the  commer- 
cial methods  of  applying  heat  treatment  to 'castings  have 
been  considered  in  preceding  chapters,  it  may  be  well  to  correlate 
the  scientific  principles  and  commercial  equipment  with  a  view 
to  providing  a  more  definite  practical  understanding  of  the  art 
of  annealing. 

It  has  been  repeatedly  stated  in  the  chapters  of  this  book 
that  annealing  consists  primarily  of  the  conversion  of  the 
metastable  system  Fe-Fe3C  into  the  stable  system  Fe-C.  This 
involves  no  change  of  chemical  composition  and  is  not  the 
effect  of  any  chemical  action  on  the  iron  by  packing,  furnace 
gas  or  other  substances.  The  only  chemical  reaction  involved 
takes  place  within  the  iron  carbide  or  cementite  of  the  iron 
and  involves  only  the  chemical  elements  present  within  the  iron, 
in  unaltered  amount  before  and  after  the  reaction : 

Fe3C  =  3Fe  +  C 

The  reaction  involves  the  absorption  of  heat  (8940  small 
calories  per  gram  molecule)  and  hence  the  reaction  will  con- 
tinue only  if  heat  be  supplied.  Recent  published  articles  have 
cast  grave  doubt  on  the  heat  of  formation  of  Fe3C.  Different  ob- 
servers do  not  even  agree  on  whether  it  is  positive  or  negative. 

In  Chap.  Ill  a  detailed  discussion  of  the  acceleration  of 
the  reaction  with  increasing  temperature  was  given  and  it  was 
pointed  out  that  the  reaction  is  necessarily  incomplete  at  all 
temperatures  above  the  lower  critical  point  of  the  final  alloy. 
The  best  and  most  recent  data  available  to  the  writer  has  been 
summarized  in  Fig.  24  in  Chapter  III  and  point  to  a  solubility  of 
free  carbon  at  Alf  considerably  less  than  the  eutectoid  ratio  of  the 
metastable  system.  Below  A^  the  solubility  apparently  becomes 
negligibly  small  but  still  existant.  No  evidence  of  a  eutectoid  of  C 
and  Fe  as  a  metallographic  entity  has  been  found. 

Metallurgically  the  purpose  of  the  annealing  treatment  is  to 
•cause  the  iron  to  traverse  such  a  temperature  cycle  as  will 

214  American   Malleable   Cast   Iron 

completely  and  most  expeditiously  transform  it  into  ferrite  and 
temper  carbon,  having  due  regard  to  the  resultant  grain 
structure  of  the  ferrite.  The  actual  heat  cycle  required  to  ac- 
complish this  result  depends  upon  the  chemical  composition 
and  previous  thermal  history  of  the  product  annealed, 

The  control  of  the  annealing  oven  to  produce  a  given  cycle 
is  further  influenced  by  the  design  of  the  furnace,  the  uniform- 
ity of  temperature  throughout,  rate  of  heating,  etc.  Therefore 
the.  art  of  annealing  cannot  be  taught  adequately  in  a  chapter 
of  a  book.  At  most  the  general  principles  may  be  outlined, 
it  being  understood  that  in  practice  the  operations  are  shaped 
toward  the  desired  end  in  accordance  with  the  skill  and  exper- 
ience of  the  annealer. 

It  already  has  been  shown  that  the  graphitizetion  of  cemen- 
tite  occurs  more  rapidly  the  higher  the  temperature  and  that  the 
rate  of  this  reaction  decreases  as  the  reaction  approaches  its 
end  point.  Consequently  at  first  glance,  it  would  seem  advan- 
tageous to  conduct  the  process  in  the  beginning  at  the  highest 
possible  temperature.  However,  there  are  practical  and  the- 
oretical objections  to  this  procedure.  The  practical  objections 
in  order  of  importance  are  as  follows : 

1.  The  extreme   warping   or   distortion   of   castings    when 
softened  by  the  high  temperature. 

2.  The  sintering  or  fusion  of  any  available  packing  ma- 
terial from  the  same  cause. 

3.  The  wear  and  tear  on  the  fire  brick  of  the  oven. 

4.  The  decreased  service  obtained   from  annealing  pots. 

5.  The    increased    fuel    cost   of    attaining    extremely    high 

The   theoretical   reasons    are   even    more   important,    being: 

1.  The  large  flaky  character  of  the  free  carbon  crystalliz- 
ing out  at  the  higher  temperatures. 

2.  The  poor  ferrite  structure  set  up  under  these  circum- 

Accordingly  the  metallurgist  must  determine  for  himself 
where  the  best  balance  between  speed  and  quality  may  lie,  hav- 
ing regard  to  the  alloys  with  which  he  has  to  work.  Opinions 
vary  somewhat  but  the  advantageous  maximum  of  temperature 
of  castings,  as  distinguished  from  furnace  atmosphere  or  wall 

Principles  of  Annealing  215 

temperature,  lies  between  1500  and  1700  degrees  Fahr.  While 
graphitization  can  be  initiated  at  temperatures  far  below  1500 
degrees,  the  reaction  at  these  lower  temperatures  is  prohibitively 
slow  without  any  compensating  advantages.  Few  packings  can 
be  found  which  will  withstand  temperatures  in  excess  of  those 
occurring  when  heating  castings  to  above  1700  degrees  Fahr. 
Moreover,  the  effect  on  grain  structure  begins  to  make  itself 
felt  at  this  temperature. 

The  reaction  at  1800  or  1900  degrees  Fahr,  is  not  sufficient- 
ly faster  to  warrant  incurring  the  increasing  difficulties  which 
present  themselves  above  1700  degrees.  Many  malleable  oper- 
ators feel  that  the  extra  time  required  to  anneal  at  temperatures 
not  exceeding  1600  degrees  is  well  spent. 

A  safe  maximum  temperature  having  been  determined  for 
the  particular  product  under  consideration,  the  annealer  first 
directs  his  attention  to  attaining  this  temperature  as  rapidly  as 
possible  consistent  with  a  reasonable  uniformity  of  temperature 
throughout  the  oven.  It  is  here  that  oven  design  influences  the 
economy  and  quality  of  the  annealing  operations. 

It  is  unavoidable  that  those  pots  nearest  the  source  of  heat 
will  heat  more  rapidly  than  the  rest.  However,  if  a  furnace  is 
designed  to  permit  the  rapid  and  free  circulation  of  flame,  the 
differences  of  temperature  will  be  far  less  than  where  such  cir- 
culation is  hindered  to  some  extent. 

All  commercial  furnaces  have  the  heat  supplied  above  the 
pots  and  all  well  designed  furnaces  have  a  sufficient  height  of 
roof  to  permit  the  flame  to  reach  freely  to  the  tops  of  the 
farthest  pots.  The  author  has  never  heard  any  annealer  ques- 
tion the  reason  for  introducing  tlie  heat  at  the  top,  all  seeming 
to  take  this  arrangement  for  granted.  However,  there  is  a 
good  scientific  reason  for  this  design.  The  heating  of  the  fur- 
nace contents  is  accomplished  mainly  by  the  vertical  gas  currents 
in  the  spaces  between  the  several  stacks  of  pots  and  to  a  minor 
extent  by  conduction  downward  through  the  pot  and  contents. 
If  two  of  the  vertical  passages  between  the  pots  are  at  different 
temperatures,  a  gas  current  will  be  set  up  rising  in  the  hotter 
and  descending  in  the  colder  of  the  two.  Therefore,  if  the  hot 


American   Malleable    Cast   Iron 

Principles  of  Annealing 


S  >5*  ^ 


•ttti ' 



^  it  ^  >i 

r\  iM)     N   V? 




218    American  Malleable  Cast  Iron 

gas  enters  at  the  top,  this  circulation  will  tend  to  divert  the 
descending  hot  gas  from  the  hotter  passages  toward  the  colder 
spaces  and  thus  heat  the  latter  more  rapidly.  Were  the  heat 
admitted  at  the  bottom  the. circulation  described  would  cause  an  in- 
crease in  the  difference  of  temperature  between  the  hot  and  cold 
passages  since  the  ascending  current  in  the  hotter  space  would 
draw  the  hot  incoming  gases  with  it. 

Time  of  Heating  Varies  Widely 

The  rapidity  with  which  an  oven  can  be  heated  uniformly 
depends  entirely  upon  its  construction.  A  number  of  observers 
have  recorded  heating,  cycles  with  pulverized  fuel  as  short  as 
18  hours,  whereas  the  author  frequently  has  witnessed  periods 
as  long  as  100  hours  and  over,  usually  under  adverse  fuel  condi- 
tions. In  some  cases  the  increased  time  is  due  to  the  impos- 
sibility of  burning  the  coal  rapidly,  while  in  others  the  rate  of 
downward  distribution  of  the  heat  in  the  furnace  is  the  limiting 
factor.  In  the  latter  case  it  sometimes  is  necessary  almost  to 
cease  firing  and  allow  the  heat  to  equalize  by  conduction  and 
radiation  in  order  to  avoid  overheating  the  top  pots.  This  pro- 
cedure is  sound  metallurgically  but  necessarily  involves  a  waste 
of  time. 

The  desired  maximum  temperature  having  been  reached 
as  uniformly  and  rapidly  as  possible,  the  next  step  is  to  main- 
tain this  temperature  until  the  reactions  within  the  castings 
have  attained  a  state  of  equilibrium.  This  time  depends  upon 
the  temperature  chosen  and  upon  the  chemical  and  structural 
characteristics  of  the  metal.  In  experimental  determinations  the 
time  to  reach  actual  equilibrium  is  long.  Under  favorable  con- 
ditions it  may  be  20  or  30  hours  at  1900  degrees,  100  to  150 
hours  at  1500  degrees  and  several  hundred  hours  at  1400  de- 
grees. In  practice  the  times  are  materially  shorter  because  a 
slight  graphitization  of  cementite  may  be  relied  upon  in  cooling 
through  the  higher  ranges  of  temperature  and  also  because 
equilibrium  is  approached  more  rapidly  during  the  earlier  stages 
than  when  it  is  nearly  attained.  Indeed  it  might  be  said  that 
actual  equilibrium  is  attained  only  in  infinite  time  at  any  tem- 
perature. Under  fairly  favorable  conditions  in  well  conducted 
plants  the  time  to  reach  equilibrium  within  commercial  limits 

Principles  of  Annealing 219 

may  be  roughly  as  follows:  1700  degrees,  25  hours;  1500, 
50  hours,  and  1450,  80  hours  or  possibly  50  per  cent  more 
under  less  favorable  conditions. 

These  general  relationships  already  have  been  indicated  in 
graphic  form  in  Fig.  36  in  Chap.  III.  The  time  required 
is  approximately  inversely  proportional  to  the  temperature 
above  A^  for  alloys  high  in  carbon  or  silicon  the  time  required 
is  less  than  for  those  lower  in  these  elements.  The  presence  of 
excessive  manganese  or  sulphur,  or  of  some  of  the  more  un- 
usual elements  may  prolong  the  time  considerably.  Also  it  is 
believed  that  the  rate  of  freezing  and  possible  other  variables 
in  the  previous  thermal  history  of  the  metal  have  an  effect  upon 
the  rate  of  graphitization. 

The  combined  carbon  content  at  equilibrium  is  greater 
the  higher  the  temperature,  therefore  the  iron  is  not  completely 
annealed  at  the  expiration  of  the  required  time  at  the  maximum 
temperature  chosen.  The  carbon  content,  or  solubility  of  carbon, 
as  dependent  on  temperature  has  been  definitely  determined  for 
metal  containing  about  1  per  cent  silicon.  The  relation  is  shown 
in  Fig.  24.  Therefore  the  anneal  will  not  be  complete  unless  the 
reaction  is  allowed  to  progress  to  equilibrium  at  or  just  under 
A\\.  The  Ar-L  point  in  commercial  iron  probably  is  between  1340 
and  1375  degrees  Fahr. 

Approach  Temperature  Slowly 

One  way  to  accomplish  the  desired  result  would  be  to  drop 
the  temperature  quickly  from  the  maximum  to  just  under  Ar±  when 
the  reaction  at  the  former  temperature  is  complete  and  to  main- 
tain that  temperature  below  Ar^  as  long  as  may  be  required  to 
re-establish  equilibrium  at  the  lower  temperature.  This  opera- 
tion will  readily  yield  perfectly  annealed  material  but  is  difficult 
to  execute  in  practice  except  possibly  in  tunnel  furnaces.  Under 
commercial  conditions,  equilibrium  can  be  attained  more 
readily  just  under  Ar^  by  approaching  this  slowly  from  above 
at  a  rate  permitting  the  graphitization  to  just  keep  pace  with 
the  falling  temperature  than  by  a  quick  drop  and  a  long  wait  to 
establish  equilibrium.  Rates  of  cooling  between  four  and  10 
degrees  per  hour  usually  are  desired  and  most  operators  prefer 
to  cool  more  and  more  slowly  as  the  temperature  drops. 

220  American  Malleable  Cast  Iron 

To  make  sure  of  attaining  equilibrium  a  number  of  an- 
nealers  wisely  attempt  to  hold  a  constant  temperature  just  under 
Ar±  for  some  time.  Nothing  is  gained  by  additional  slow  cool- 
ing after  the  reaction  at  Ar±  is  complete. 

In  many  plants  the  cooling  rate  is  determined  by  the  heat 
radiation  of  the  furnace.  In  these  cases  the  annealer  merely 
seals  the  furnace  at  the  high  temperature  and  lets  it  take  care 
of  itself.  Fortunately,  since  the  rate  of  cooling  decreases  as  the 
temperature  of  the  oven  falls,  a  well  insulated  furnace  cooling 
naturally  will  fall  in  temperature  at  a  steadily  decreasing  rate, 
as  the  metallurgical  theory  required.  Therefore  the  results  of 
this  practice  often  are  much  better  than  might  be  expected. 
Difficulties  begin  to  arise  when  the  cooling  is  accelerated  by 
some  unforeseen  or  unknown  cause  and  the  illogical  operator 
is  no  longer  able  to  account  for  his  results. 

It  will  be  noticed  that  a  complete  annealing  cycle  may  be 
subdivided  into  five  distinct  intervals  as  follows:  Heating  to 
maximum  temperature,  maintaining  maximum  temperature  till 
equilibrium  is  attained  in  graphitization  of  cementite,  cooling 
to  critical  point,  holding  just  under  the  critical  point,  and  further 
cooling  to  permit  handling. 

The  first  and  last  periods  have  no  metallurgical  significance 
and  can  be  accelerated  as  much  as  is  convenient.  However, 
the  second  and  the  combination  of  the  third  and  fourth,  are 
determined  by  the  product  being  manufactured  and  cannot  be 
reduced  below  definite  minimum  values.  The  minimum  cycle 
is  divided  as  follows:  Heating  to  1600  degrees,  30  hours; 
holding  at  1600  degrees  45  hours;  cooling  to  Ar^  and  holding 
there,  35  hours;  and  cooling  to  handle,  5  hours.  The  total  is 
115  hours,  which  would  make  a  six-day  annealing  cycle  as  an 
absolute  minimum,  the  time  above  115  hours  being  spent  in 
charging  and  pulling.  However,  few  plants  are  able  to  insure 
success  in  so  short  a  cycle  and  seven  days  may  be  considered 
as  the  commercial  minimum.  Cycles  of  nine  days  and  more  are 
not  uncommon  with  large  furnaces  in  order  to  secure  the  best 

The  minimum  annealing  time  is  fixed  by  natural  laws  which 
cannot  be  changed  to  suit  the  wishes  of  the  manufacturer  or 

Principles  of  Annealing  221 

the  consumer.  Any  attempt  on  the  part  of  the  user  to  hurry 
the  producer  is  misguided.  The  response  to  such  pressure  will 
be  in  inverse  ratio  to  the  conscientiousness  and  intelligence  of 
the  particular  manufacturer  concerned.  It  would  seem  that 
self  interest  will  drive  the  malleable  founder  to  adopt  the 
shortest  workable  annealing  cycle  in  order  to  avoid  the  in- 
vestment in  additional  ovens  and  their  fuel  supply.  Nevertheless 
the  author  has  known  many  purchasers  of  malleable  who 
seemed  to  regard  the  operation  of  a  long  cycle  as  an  arbitrary 
wish  of  the  manufacturer  imposed  upon  his  customer  without 
any  adequate  reason. 

For  many  years  the  larger  producing  interests  have  been 
approached  from  time  to  time  by  frequently  sincere  but  always 
poorly  informed  inventors  claiming  either  to  much  reduce  an- 
nealing time  or  sometimes  to  do  away  with  annealing  entirely. 
As  a  rule,  those  in  the  former  class  expect  to  accomplish  results 
by  changes  either  in  furnace  design,  methods  of  heating,  etc.,  or 
by  some  unusual  and  often  secret  packing.  Being  an  atomic  re- 
arrangement within  the  metal  itself,  the  annealing  reaction  can- 
not be  accelerated  or  retarded  by  the  material  surrounding  the 

The  laws  governing  graphitization  have  been  investigated 
by  a  number  of  entirely  competent  experimenters  and  depend 
on  clearly  known  chemical  fundamentals.  The  design  of  heat 
treating  furnaces  also  is  well  understood.  Changes  in  furnace 
design  could  only  reduce  the  annealing  time  by  accelerating  the 
time  of  heating,  since  as  already  explained,  the  times  and  tem- 
peratures during  the  rest  of  the  cycle  are  fixed  by  the  metal  be- 
ing annealed.  All  of  these  patented  or  secret  annealing  methods 
therefore  are  foredoomed  to  failure. 

It  is  conceivable,  although  improbable,  that  someone  will 
discover  an  alloy  with  a  carbon  content,  similar  to  that  now 
used,  of  such  a  character  that  graphitization.  will  be  suppressed 
at  temperatures  above  1600  degrees  Fahr.  but  which  will  graphi- 
tize  easily  or  even  spontaneously  at  lower  temperatures.  Such 
an  invention  would  accelerate  or  eliminate  the  present  annealing 
process.  Since  the  alloys  of  iron  with  most  of  the  reasonably 
common  elements  are  constantly  being  investigated  and  no  indi- 

222  American  Malleable   Cast  Iron 

cations  have  been  found  of  any  elements  with  properties  pro- 
ducing the  complex  effect  here  described  in  any  degree,  it 
seems  most  unlikely  that  any  greatly  accelerated  annealing  meth- 
od for  producing  black  heart  malleable  will  be  found. 

Therefore  producers  and  consumers  should  admit  the 
necessity  of  adequate  time  for  annealing  and  conduct  their 
several  operations  in  accordance.  The  author  is  still  waiting 
to  hear  from  a  most  enthusiastic  engineer  who,  three  months 
before  this  was  written,  offered  to  demonstrate  the  manufacturer's 
ignorance  of  annealing  principles  by  taking  home  a  sample  of 
hard  iron  in  the  evening,  annealing  it  over  night  and  returning 
it  completely  annealed  the  next  day. 

Other  incidental  changes  are  produced  in  the  metal  while 
graphitization  is  going  an.  The  clearest  evidence  that  these 
changes  are  only  incidental  is  the  fact  that  the  process  of 
graphitization  can  be  carried  on  perfectly  without  any  gain  or 
loss  of  weight.  To  prove  this,  an  accurately  weighed  speci- 
men of  hard  iron  can  be  enclosed  in  a  tube  of  difficultly  fusible 
glass,  the  air  displaced  by  hydrogen,  the  hydrogen  pumped  out 
to  a  fairly  low  pressure  and  the  tube  then  sealed,  so  that  the 
metal  can  be  annealed  surrounded  by  nothing  but  a  trace  of  a 
reducing  gas.  Samples  of  10  or  12  grams  weight  annealed  in 
such  a  tube  in  accordance  with  the  heat  cycle  of  commercial 
practice,  are  unaltered  in  weight  to  1/10  milligram.  In  other 
words,  the  weight  remains  constant  to  1/1000  of  1  per  cent. 

Migration  of  Carbon 

However,  under  commercial  conditions  the  castings  always 
are  in  an  atmosphere  having  oxidizing  possibilities.  This  at- 
mosphere may  be  the  atmospheric  air  remaining  in  the  spaces 
not  otherwise  occupied  or  it  may  be  the  products  of  combustion 
or  gases  arising  from  reactions  with  packing  materials.  There- 
fore there  always  is  a  tendency  toward  burning  out  the  surface 
carbon.  The  mechanism  of  the  removal  is  interesting.  Only 
the  carbon  in  the  outer  layer  of  molecules  can  combine  directly 
with  any  oxygen  in  the  surrounding  gas.  Therefore  unless 
either  the  gas  can  penetrate  the  solid  metal  or  the  carbon  can 
migrate  to  the  surface,  decarburization  would  be  limited  to  the 

Principles  of  Annealing 


infinitesimally  small  amount  produced  by  burning  out  the  car- 
bon one  molecule  deep. 

At  one  time  it  was  generally  believed  that  the  gas  penetrates 
but  the   migratory  action   certainly  exists   and   is   probably   the 

.01    .oa    .03  .04  .05-  .06  .07  .06  .09    .10   .// 

Inches  Be/ow  Surface 

Fig.   99— Increase  in   carbon  content  at  increasing   depths   below   the   sur- 
face  of    malleable    cast   iron 

major  method  by  which  carbon  and  oxygen  are  brought  to- 
gether. Carbon  exists  in  iron  at  any  temperature  above  Acz 
in  part,  as  a  solid  solution  of  a  definite  saturation  value  at  any 
given  temperature.  If  the  carbon  concentration  is  locally  low- 
ered below  saturation,  diffusion  will  enrich  this  area  at  the  ex- 
pense of  the  more  highly  carburized  areas.  So  long  as  ce- 
mentite,  or  undissolved  iron  carbide  remains,  the  deficit  will 

224 American  Malleable   Cast  Iron : 

be  made  up  by  solution  of  additional  amounts  of  this  element 
in  such  a  quantity  as  to  maintain  the  solid  solution  in  a  saturated 

This  migration  requires  considerable  time  so  that  in  gen- 
eral, carbon  is  oxidized  at  the  surface  much  more  rapidly  than 
diffusion  can  equalize  the  carbon  content.  The  result  is  a  ma- 
terial poorer  in  carbon  at  the  surface  than  in  the  center.  As 
we  go  further  toward  the  center,  the  increase  in  carbon  content 
corresponds  to  a  sort  of  gradient  which  is  sufficient  to  feed  the 
carbon  to  the  surface  as  fast  as  it  is  removed. 

Fig.  99  shows  the  increase  in  carbon  content  at  increasing 
depths  below  the  surface.  The  graphs  represent  various  de- 
grees of  decarburization  under  commercial  operating  conditions. 
It  will  be  noted  that  the  graphs  vary  both  as  to  carbon  con- 
centration at  the  surface  and  as  to  the  depth  of  penetration. 
The  former  depends  somewhat  on  the  oxidizing  medium  em- 
ployed, the  latter  on  the  length  of  time,  the  medium  is  applied, 
and  on  its  activity. 

The  effect  of  this  decarburization  on  the  physical  properties 
of  the  product  are  relatively  small.  Fig.  100  shows  graphically 
the  results  of  careful  tests  made  to  determine  the  effect  of  the 
removal  of  1/16  inch  of  carburized  surface  in  specimens  of 
various  diameters  on  the  tensile  properties  of  the  metal.  The 
experiments  were  conducted  by  casting  tensile  specimens  to  a 
series  of  diameters,  grinding  one  specimen  of  each  size  truly 
cylindrical,  removing  about  1/16  inch  of  stock.  The  ground 
specimens  then  were  annealed  with  rough  specimens  from 
the  same  heat  and  turned  to  size  after  annealing.  The  graphs 
show  the  amount  by  which  the  properties  of  the  specimen  ground 
before  annealing  exceeds  the  corresponding  properties  of  the 
turned  specimens. 

The  experiment  was  conducted  in  this  form  to  eliminate 
variations  due  to  cooling  rate  and  original  rough  surface  which 
variables  are  included  in  the  data  given  in  the  chapter  on  tensile 

The  tests  were  conducted  on  one  lot  of  metal,  all  annealed 
together.  Therefore  they  correspond  to  one  set  of  decarburiz- 

Principles  of  Annealing 


ing  conditions  only.  Since  decarburization  varies,  as  the  an- 
nealing conditions  vary,  another  series  of  investigations  was 
made  to  determine  the  changes  in  properties  in  iron  of  initially 
similar  composition  by  variable  decarburization. 

D/omefer  Of  Specimen  Inches 

Fig.    100 — Graph    showing    effect    of    removing    1/16    inch    decarburized 

surface  in  specimens  of  various  diameters  on  the  tensile 

properties    of    the   metal 

-  Results  of  50  Tests 

In  Fig.  101  have  been  plotted  the  results  of  some  50  such 
tests  on  iron  having  from  2.40  to  2.60  per  cent  carbon,  0.70  to 
0.80  per  cent  silicon  before  anneal,  which  correlate  the  tensile 
properties  with  the  carbon  content  after  annealing.  The  graph 


American  Malleable   Cast  Iron 

is  plotted  from  average  values.  Individual  tests  depart  con- 
siderably from  the  average  since  small  differences  of  carbon  con- 
tent in  the  hard  iron  affect  the  results  much  more  than  much 
larger  variations  in  this  element  due  to  decarburization. 





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Tof  a/  Carbon  Be  fore  Ann  ea/  £.&O/£^ 

on  Oxidized     /.5O        U5         WO             .7? 
*orbon  After  LO       /.Z5          /.50           /,7S 

Fig.    101  —  Graph    showing    effect    of    varying    degrees    of    decarburization 
on  tensile  properties  of  malleable  cast  iron 

Figs.  100  and  101  serve  to  show  that  the  final  properties  are 
relatively  little  affected  by  the  decarburization  process.  Be- 
ing measured  on  surface  metal  the  elongation  probably  depends 
only  in  the  carbon  content  near  the  surface  and  but  little  on 
the  depth  of  decarburization.  The  tensile  properties  are  some- 
what more  consistently  affected  by  decarburization. 

Decarburization  is  controlled  in  practice  by  the  character  of 
the  packing  material.  Perhaps  it  would  be  more  accurate  to 
say  that  the  results  in  practice  depend  on  the  packing  used,  there 

Principles  of  Annealing  227 

being  but  little  available  information  with  regard  to  the  action 
of  packing. 

The  commercial  packings  depend  for  their  activity  chemically 
on  the  reduction  of  ferric  oxide,  Fe2O3  to  FeO,  ferrous  oxide. 
It  is  not  to  be  understood  that  they  actually  liberate  oxygen  on 
heating  as  for  instance  potassium  chlorate  does. 

Four  Possible  Reactions 

The  process  is  a  chemical  reaction  in  which  the  oxygen  never 
appears  as  such  but  merely  combines  with  carbon.  Four  re- 
actions are  possible,  depending  upon  the  circumstances: 

3  Fe2O3  +  Fe3C  =  2  Fe3O4  +  CO  +  3  Fe 

6  Fe2O3  +  Fe3C  =  4  Fe3O4  -f  CO2  +  3  Fe 

Fe3O4  +  Fe3C  =  3  Fe  O    +  CO    -f  3  Fe 

2  Fe3O4  +  Fe3C  =  6  Fe  O    +  CO2  +  3  Fe 

The  two  reactions 'FeO+Fe3C=Fe+CO+3Fe  and  2  FeO 
-J-Fe3C=2Fe+CO2+3Fe  are  theoretically  possible  but  occur 
only  under  unusual  circumstances,  if  at  all. 

The  reaction  3FeO+50O— Fe3C+4CO2  can  probably  oc- 
cur under  certain  unusual  conditions. 

The  fact  that  the  analysis  of  packings  is  expressed  as  a 
rule  in  terms  of  the  Fe2O3  FeO,  SiO2  and  possibly  A12O3  and 
other  oxides  has  given  rise  to  the  unfortunate  conception  that 
they  are  mixtures  of  two  oxides  of  iron  with  other  inert  oxides. 
As  a  matter  of  fact  all  packings  in  use,  as  distinguished  from 
the  raw  packing,  have  become  complex  silicates.  The  practical 
annealer  unconsciously  acts  on  this  knowledge  where  he  limits 
his  additions  of  roll  scale,  or  other  raw  material  to  small 
amounts  at  any  one  time,  for  a  packing  containing  any  large 
amount  of  free  oxides  is  not  a  workable  material. 

The  raw  material  from  which  packing  is  built  up  usually 
is  roll  scale  or  squeezer  scale  from  rolling  mills,  pot  scale  (the 
oxide  from  the.  outer  surface  of  the  annealing  pots  after  they 
are  drawn  from  the  furnace)  or  air  furnace  slag.  Iron  ore  was 
once  used  but  probably  is  now  obsolete.  Table  XVI  shows  the 
composition  in  the  usual  terms,  of  these  several  materials. 

It  should  be  understood,  however,  that  only  the  first  three 
are  actually  oxides.  Ore  is  nearly  pure  ferric  oxide  contam- 

228 American  Malleable  Cast  Iron 

Table  XVI 


FeO  Fe203  MnO      SiO,       A1,O, 

Ore    00  91.43  8.57 

Pot  scale   37.10  53.11  9.79 

Roll    Scale    61.47  31.99  6.54 

Squeezer    scale    69.74  9.34  .80        14.95          5.17 

Slag     28.80  1.16  4.85        50.42        14.77 

inated  somewhat  with  silica  minerals.  Pot  scale  is  a  more  or 
less  impure  magnetic  oxide,  Fe3O4  contaminated  by  sand  adher- 
ing to  the  pots.  Roll  scale  is  magnetic  and  ferrous  oxide 
originally  nearly  pure,  but  contaminated  in  gathering  it  up  and 
shipping.  Squeezer  scale  is  a  mixture  of  basic  silicates  of  iron 
and  manganese  with  some  iron  oxides,  mainly  ferrous  oxide 
dissolved  in  bibasic  ferrous  silicates.  Slag  is  a  neutral  silicate 
contaminated  with  fused  brick,  etc. 

Some  typical  analyses  of  packings  as  actually  used  are 
shown  in  Table  XVII  both  in  terms  of  the  usual  proximate 
analysis  and  in  terms  of  the  compounds  apparently  present. 

It  will  be  seen  that  the  packings  contain  little  free  oxide 
and  are  mainly  silicates.  The  ferrous  silicates  are  incapable  of 
reduction  to  metallic  iron  under  the  usual  annealing  conditions 
so  that  the  oxygen  for  oxidizing  the  carbon  is  derived  primarily 
from  the  reduction  of  Fe2O3  to  FeO  although  the  ferrous  oxide 
of  pot  and  roll  scale  may  enter  into  the  reaction. 

The  relative  amounts  of  carbon  monoxide  and  carbon  di- 
oxide formed  depend  on  the  temperature  and  the  packing  used. 
With  the  materials  and  temperature  of  commercial  practice  the 
ratio  is  fairly  constant;  approximately  12J^  per  cent  of  the  car- 
bon being  burned  to  CO2  the  remainder  to  CO. 

The  principal  reaction  involved,  assuming  Fe2O3  as  the  ac- 
tive medium,  corresponds  to  the  equation: 

9  Fe2O$  -f  8  Fe8C  =  18  FeO  +  7  CO  +  COa  +  24  Fe 

The  actual  mechanism  of  the  decarburizing  reaction  forms 
an  interesting  though  complex  problem  in  physical'  chemistry. 
The  oxidation  of  the  carbon  in  the  iron  and  reduction  of  the 

Principles  of  Annealing 229 

packing  are  accomplished  by  the  gas  surrounding  both.  To  be 
operative,  a  system  must  be  chosen  so  that  at  the  temperature 
and  pressure  in  the  .annealing  pot  the  gas  phase  present  is  such 
that  the  reactions 

Fe3C  +  COa  =  2  CO  +  3  Fe 

Fe2O3  +  CO  +  =  2  FeO  +  COa 

FeO  +  CO  =Fe  +  COa 

can  all  proceed  from  left  to  right.  In  other  words  the  system 
must  be  one  in  which  a  ratio  of  CO  to  CO2  can  be  maintained 
which  will  at  the  same  time  oxidize  Fe3C,  reduce  Fe2O3,  and 
reduce  FeO. 

If  the  relative  concentration  of  CO  and  CO2  be  such  that 
the  first  reaction  ceases  or  reverses  no  decarburization  will 
occur.  If  the  reaction  is  initiated  it  would  soon  cease,  due  to  the 
conversion  of  all  available  CO2  to  CO,  unless  the  second  re- 
action continuously  reconverted  CO  to  CO2.  If  the  last  re- 
action reversed,  the  iron  of  the  casting  would  be  oxidized  in 
addition  to  the  carbon  in  the  consequent  scaling  .  Only  some 
of  the  more  usual  reactions  have  been  considered  there  being  a 

Table  XVII 


Source  Pot  scale         Roll  scale      Squeezer  scale        Slag 

Fe    4.04  6.88                

FeO    54.36  57.33  58.49  38.25 

Fe20s    9.04  5.97  3.14  1.03 

MnO     1.50  3.03 

SiO,     21.02  26.16  24.92  43.60 

AlaO,  and  undetermined  ..11.54  9.66  11.95  14.09 

Proximate    Composition   of  Above 

Per*  cent 

Fe                     4.04  6.88                

FeO    . 23.40  31.34  21.00  12.60 

Fe203 5.97                1.00 

(FeO)2   SiO,    40.90                56.90                

(Fe203)2     (Si02)3 ..14.10                5.40                

(FeO),  (Si02)a 27.91                ..... 

FeO  Si02   45.20 

Fe20,   (SiO,), ....  5.40 

Various  inert  silicates    by 

difference    .                    ..17.56  27.90  16.70  35.80 


American  Malleable  Cast  Iron 

number  of  others  possible  between  the  components  of   such  a 

Scientific  investigations  of  the  subject  matter  involved  would 
be  based  on  determination  of  the  composition  of  the  gas  phase 
in  equilibrium  with  the  several  oxides  of  iron  and  carbon  con- 
cerned and  a  location  as  to  temperature  and  concentration  cor- 

Fig.    102 — Equilibrium    curves    illustrating    the    reactions    between    carbon, 
iron  and  oxygen,  after  the  data  of  Matsubara 

responding  to  the  reactions  proceeding  in  the  desired  directions. 
The  subject  has  been  but  imperfectly  studied,  the  available  in- 
formation being  mainly  due  to  Schenks'  summary  "Physical 
Chemistry  of  the  Metals."  Matsubara,  in  a  paper  presented 
before  the  American  Institute  of  Mining  and  Metallurgical 
Engineers,  February,  1921,  amplifies  and  checks  Schenks'  data, 
particularly  with  respect  to  the  reactions  into  which  the  cementite 
enters  in  the  presence  of  CO  and  CO2. 

Principles  of  Annealing  231 

Fig.  102  is  drawn  from  Matsubara's  paper,  based  on  his  own 
results  as  well  as  those  of  Boucourd,  Bauer,  Schenk  and  others. 
It  represents  the  percentage  of  CO  in  a  mixture  of  CO  and  CO2 
for  various  temperatures  at  which  the  several  reactions  will 
proceed  equally  rapidly  in  both  directions — or  at  which  they 
will  cease  and  equilibrium  will  be  established.  The  graphs  are 
plotted  for  a  pressure  of  one  atmosphere  as  the  sum  of  the 
partial  pressures  of  CO  and  CO2.  For  other  pressures  the 
equilibria  can  be  calculated  from  the  equilibrium  constants  of 
the  several  reactions.  Letting  P  be  the  pressure  exerted  by 
CO  and  CO2,  X  the  amount  of  CO  in  the  mixture  of  these 
gases  and  Klf  K2  and  K3  the  equilibrium  constants  for  equations 
1,  2  and  3,  respectively,  then 


K,= P  i 

1— X 

K2= P 

K,- P 


KI  K2  and  K3  can  be  calculated  from  Fig.  102  for  any  giv- 
en temperature  and  hence  the  change  produced  in  X  by  changes 
of  pressure  at  that  temperature  can  be  calculated  and  a  dia- 
gram similar  to  Fig.  102  constructed  for  other  pressures. 

Reaction  (4)  and  (5)  are  independent  of  pressure.  Un- 
fortunately nothing  is  known  as  to  the  locus  of  the  curves  cor- 
responding to  (4)  and  (5)  for  the  silicates  forming  commer- 
cial packings.  The  interpretation  of  the  equilibrium  diagram 
to  determine  what  reactions  occur  is  as  follows: 

On  areas  below  (3)  cementite  is  oxidized  to  FeO  and  CO; 
in  areas  above  (4)  FeO  is  reduced  to  Fe  with  the  formation 
of  CO2,  hence  in  any  region  below  (3)  and  above  (4),  FeO 
will  oxidize  the  carbon  of  cementite.  Such  regions  exist  only 
above  700  degrees  Cent.,  therefore  the  reaction  cannot  be  main- 
tained at  lower  temperatures.  That  the  lines  (1),  (2),  (3)  and 
(4)  should  intersect  at  one  point  is  curious,  and  indicates  that 
at  that  temperature,  pressure  and  composition,  C,  Fe,  FeO  and 
Fe3C  or  any  two  or  more  of  these  radicals  can  exist  together 

232 American  Malleable  Cast  Iron 

in  equilibrium.  Almost  any  question  as  to  the  course  of  the 
annealing  reaction  or  the  behavior  of  packings  could  be  answered 
.by  the  construction  of  such  diagrams  for  the  particular  packing 
material.  Many  conclusions  as  to  the  reactions  of  the  pure  ele- 
ments and  their  oxides  and  carbides  will  present  themselves  on 
further  study  of  the  diagrams. 



IN  MANY  respects,  patternmaking  and  molding  practice  in 
malleable  plants  does  not  differ  from  that  in  other  branches 
of  the  foundry  industry.  The  various  devices  adopted  for 
repetitive  work  in  gray  iron  or  brass  also  are  found  in  use  in 
the  malleable  shop.  Indeed,  since  the  producers  of  malleable 
engage  largely  in  the  manufacture  of  small  and  moderate  sized 
parts  in  large  numbers  the  development  perhaps  is  further  ad- 
vanced than  in  gray  iron  practice.  However,  there  are  certain 
vital  differences  between  patternmaking  and  molding  for  mal- 
leable cast  iron  as  distinguished  from  the  same  operations  in 
the  gray  iron  trade.  These  differences  arise  from  the  metal- 
lurgical properties  of  the  two  materials. 

The  two  essential  distinctions  between  white  iron  and  gray 
iron  lies  in  the  melting  point  and  shrinkage  of  the  two  metals. 
Gray  iron  castings  of  moderate  size  are  made  of  metal  con- 
taining, for  example,  3.25  per  cent  carbon,  2.00  silicon  and  0.50 
phosphorus  as  compared  with  the  composition  of  white  cast  iron 
which  approximates  2.50  per  cent  carbon,  0.75  silicon  and  0.19 
phosphorus.  The  equilibrium  diagram  for  the  iron  carbon 
alloys  shows  that  all  alloys  above  2  per  cent  in  carbon  finish, 
freezing  at  the  same  temperature — 1130  degrees  Cent,  or  2066 
degrees  Fahr.  It  shows  further  that  the  point  where  freezing 
begins  varies  with  the  carbon,  decreasing  nearly  uniformly  from 
1550  to  1130  degrees  Cent,  as  the  carbon  increases  from  nothing 
to  4.3  per  cent. 

Leaving  the  other  elements  out  of  consideration,  the  white 
iron  should  begin  to  freeze  at  roughly  1310  degrees  Cent,  or 
2390  degrees  Fahr.  and  the  gray  iron  at  1220  degrees  Cent,  or 
2250  degrees  Fahr. 

Thus  gray  iron  will  be  completely  liquid  at  a  temperature 
140  degrees  Fahr.  lower  than  that  at  which  white  cast  iron  has 
begun  to  solidify  and  .the  range  of  partial  solidification  or  pasti- 


American  Malleable    Cast  Iron 

ness  is  larger  by  that  amount  in  white  cast  iron  than  in  gray 

The  presence  of  silicon  still  further  accentuates  this  point. 
According  to  Gontermann's  data,  metal  of  the  composition  as- 
sumed for  gray  iron  should  begin  to  freeze  at  about  1200  de- 

Fig.  103— (Above)   Two  gates  of  metal  patterns  in  match  part;    (below) 

Pattern   mounted   on   match   plate  and   gated  pattern 

mounted  on  vibrator  frame 

grees  Cent,  or  2190  degrees  Fahr.  and  be  completely  frozen  al 
1140  degrees  Cent,  or  2080  degrees  Fahr.,  whereas  white  cast 
iron  should  begin  to  freeze  at  1330  degrees  Cent,  or  2420  de- 
grees Fahr.  and  finish  the  process  at  1170  degrees  Cent,  or  2140 
degrees  Fahr. 

The  data  are  not  exactly  in  accord  with  those  based  on  car- 

Patternmaking  and  Molding  235 

bon  alone,  due  to  minor  differences  in  the  observations  on  which 
the  data  were  based.  The  point  to  be  clearly  brought 'out  is 
the  higher  point  of  incipient  freezing  and  longer  partially  frozen 
range  for  white  cast  iron  than  for  gray  iron.  The  presence 
of  phosphorus  in  larger  amount  in  the  latter  still  further 
accentuates  the  difference,  although  the  writer  has  no  available 
data  on  the  freezing  conditions  in  the  system  Fe-Si-P-0. 

The  data  given  show  clearly  that  white  cast  iron  must  be 
poured  at  a  much  higher  temperature  than  gray  iron,  since 
the  latter  will  be  liquid  at  a  temperature  perhaps  230  degrees 
Fahr.  below  that  where  the  former  has  begun  to  set.  Further- 
more, it  is  quite  possible  that  the  fluidity  of  white  iron  when 
at  a  temperature  say  100  degrees  Fahr.  above  its  freezing  point 
is  materially  less  than  that  of  gray  iron  at  the  same  temperature 
above  its  freezing  point. 

Within  the  author's  knowledge  data  on  this  point  are 
lacking.  A  further  corollary  of  the  difference  in  freezing 
conditions  is  that  other  things  being  equal  there  will  be  more 
shrinks  or  porous  areas  in  white  than  in  gray  iron  castings. 
This  arises  from  the  longer  freezing  range  of  the  former  corres- 
ponding to  a  larger  fluid  contraction  of  the  still  liquid  alloy 
between  the  time  and  temperature  of  incipient  and  complete 
solidification.  The  consequence  of  this  increased  fluid,  contrac- 
tion is  that  as  the  temperature  of  complete  freezing  is  ap- 
proached there  no  longer  remains  a  sufficient  volume  of  liquid 
to  fill  the  voids  in  the  previously  formed  solid  skeleton. 

Therefore,  in  the  last  freezing  areas,  voids  remain  between 
the  dendritic  crystals  of  the  first  frozen  solid. 

The  shorter  the  freezing  range  the  less  of  this  contraction 
can  occur.  It  has  been  shown  by  Cesaro  that  liquid  iron  is 
a  solution  of  cementite  in  iron  and  Wust  and  Peterson  have 
demonstrated  that  all  such  alloys  freeze  as  cementite  and 
austenite.  However,  in  the  temperature  interval  just  under 
freezing  the  higher  silicon  and  carbon  metals  graphitize  by 
the  conversion  of  cementite  into  iron  and  carbon. 


American  Malleable    Cast   Iron 

Fig.    104 — Hand    operated    squeezer-type    molding    machine    and    (below) 

mold  and  pattern  equipment  in  position  on  machine.     Heavier 

machines  operated  by  air  also  are  used  in  the  industry 

Patternmaking  and  Molding  237 

The  iron  resulting  from  this  reaction  occupies  almost 
the  same  volume  as  the  original  cementite.  The  total  volume 
therefore  is  increased  almost  by  the  volume  of  carbon  liberated. 
As  a  consequence  there  is  a  tendency  to  expansion  at  these  high- 
er temperatures.  A  number  of  observers  especially  Turner  have 
recorded  actual  increase  in  linear  dimensions  while  the  metal 
was  cooling  and  therefore  contracting,  just  under  the  freezing 

The  expansion  due  to  graphitization  is  important  in  two 
respects.  It  causes  the  casting  to  be  only  about  1  per  cent 
smaller  in  linear  dimensions  (3  per  cent  by  volume)  than  the 
pattern  instead  of  double  these  values  for  white  iron,  and  also 
tends  to  fill  up  in  part  the  voids  left  by  fluid  contraction. 

The  difference  in  pattern  equipment  and  molding  methods 
in  the  malleable  as  compared  with  gray  iron  industries  is  due 
to  the  necessity  for  providing  against  the  following  differences 
in  the  properties  of  the  two  metals. 

1.  The  higher  melting  point  and  lower  fluidity  of  white 

2.  Its  greater  tendency  to  internal  shrinkage  due  to  fluid 

3.  Its  greater  shrinkage  from  pattern  size. 

It  will  be  noticed  that  the  noun  "shrinkage"  has  two 
distinct  but  related  meanings  to  foundrymen.  One  refers  to 
the  reduction  in  the  overall  dimensions  of  the  casting  as  com- 
pared with  the  pattern  and  the  other  to  the  production  of 
porosities  due  to  voids  left  by  the  contraction  of  the  fluid  metal. 

A  distinction  based  on  the  words  "solid  contraction"  and 
"fluid  contraction"  seems  desirable  but  has  not-  gained  favor 
among  foundrymen.  Accordingly  one  must  be  constantly  on 
the  alert  to  avoid  confusion  due  to  the  indiscriminate  use  of  the 
term  "shrinkage." 

Speaking  first  of  this  property  in  the  sense  of  solid  con- 
traction, the  fact  that  the  shrinkage  of  white  iron  is  about  ^4 -inch 


American   Malleable   Cast  Iron 

Fig.    105 — Stripper    and    roll-over    molding    machines 

(Top)  Plain  stripper  plate  molding  machine  and  equipment  for  cope  and  drag. 
(Center)  Roll-over  machine  for  drag.  The  cope  is  rammed  up  from  a  plain  plate. 
(Bottom)  Stripper  plate  machine  for  cope  and  a  roll-over  machine  for  the  drag. 

Patternmaking  and  Molding 


per  foot  instead  of  ^ -inch  per  foot  as  in  gray  iron  does  not  cause 
any  difficulty  in  patternmaking,  except  that  a  proper  allowance 
must  be  made  by  using  a  "double"  or  54 -inch  shrink  rule  in 
laying  out  the  work  in  case  the  casting  is  to  be  used  hard.  This 
shrink  rule  is  merely  a  rule  graduated  in  feet  and  inches  and 
fractions  of  inches — usually  sixteenths — in  which  the  distance 
marked  as  one  foot  is  12.25  inches.  A  casting  from  this  pattern 
will  come  from  the  mold  about  true  to  size. 

Experiment  has  shown  that  the  solid  contraction  of  white 

n  Length  in  Per  Cent  of  Length  at  75  °F. 

Co  KJ  O^  O 













Total  Contraction  Independent 
of  Chemical   Composition.Data 
on  Samples  of  at>out  2^Tbtal 
Carbon    No  Graphite 






00               1600                IZOO               800               400                0 

Temperatures,  Deq.  Fahr. 

Fig.     106. — Curve     showing     contraction    in     cooling     from     solidifica- 
tion   to   room    temperature 

cast  iron  (metastable  carbon  iron  alloys)  is  substantially  the 
same  irrespective  of  composition.  The  contraction  in  cooling 
from  solidification  to  room  temperature,  is  graphically  shown 
in  Fig.  106. 

On  annealing  the  casting  expands  due  to  the  fact  that  tem- 
per carbon  and  ferrite  occupy  a  considerably  greater  volume 
than  the  cementite  from  which  they  are  formed.  The  increase 
in  volume  and  in  linear  dimensions,  depends  primarily  on  the 
original  total  carbon  and  to  a  less  degree  on  the  heat  treatment 


American   Malleable    Cast  Iron 

by  which  the  graphitization   is  attained  and  possibly  on  other 
more  obscure  circumstances. 

Some  conclusion  as  to  the  changes  of  dimensions  produced 
by  graphitization  can  be  formed  from  the  following  density 
data:  Ferrite  7.90,  cementite  7.438,  carbon  2.30  to  2.70. 

Dimensions  Determined  by  Trial 

The  expansion  in  annealing  is  usually  assumed  to  be  one- 
half  the  original  contraction  making  the  net  "shrinkage"  allow- 
ance Y%  inch  per  foot  as  for  gray  iron.  This  conclusion  can  be 
correct  for  only  one  particular  carbon  content.  It  was  probably 





























1.0                 1.10                1.20                130               1.40                1.50               1.60 
Per  Cent  Contraction  of  Malleable  Specimanfrom  Pattern  Size 

Fig.    107 — Graph    showing    the    per    cent    of    contraction   of   malleable 

from  pattern  size 

fairly  accurate  in  the  days  when  high  carbon  iron  was  prevalent. 

W.  L.  Woody  has  given  the  writer  data  obtained  in  a  study 
of  over  1000  heats  from  which  test  specimens  were  cast  from 
a  pattern  12  inches  long,  the  specimens  being  micrometered 
after  annealing.  The  results  are  shown  graphically  in  Fig.  107. 
The  percentage  of  net  shrinkage  of  unconstrained  specimens  read  from  this  graph. 

The  author  has  determined  the  density  of  hard  iron  and 
malleable  cast  iron  made  therefrom  for  various  carbon  contents. 

Patternmaking  and  Molding 


The  data  are  shown  in  Fig.  108  calculations  as  to  change  of  di- 
mensions in  annealing  from  these  changes  in  density  yield  re- 
sults apparently  in  error  in  the  direction  of  too  much  expansion 
in  anneal,  i.e.  to  too  small  a  shrinkage  allowance. 

In  determining  pattern  dimensions  consideration  must  also 
be  given  to  the  fact  that,  due  to  rapping,  the  molds  always  are 
larger  than  the  pattern,  except  on  ''stripper  plate"  equipment. 

On  vibrator  plates  this  "rappage"  will  be  small  and  uni- 
form, in  bench  and  floor  molding  by  hand  it  will  be  variable  and 
may  be  large. 

Very  small  parts  may  actually  require  a  negative  "shrink- 








2.3  2.5  2.7  2.9 

Per  Cent  Carbon  In  Hard  Iron 


Fig.     108 — Graphs    showing    relation    of    annealing    upon    the    density 

of  the  metal 

age  allowance"  "the  rappage"  exceeding  the  solid  contraction. 
Further  it  may  happen  that  in  irregular  and  intricate  cast- 
ings some  parts  constrain  others  when  freezing  and  leave  shrink- 
age strains.  The  relief  of  these  strains  during  the  annealing 
may  cause  unexpected  changes  of  form. 

Therefore  it  often  is  necessary  to  arrive  at  the  pattern  size 
for  important  dimensions  by  actual  trial  and  even  then  the 
castings  will  come  true  to  size  only  so  long  as  temperature  of 


American  Malleable    Cast   Iron 

Pro£o£>/e  for/7?or/bn  Of  Crock 

Fig.    109 — Casting    with    thin   disk   and    thick   hub,    showing    probable 

point  of  rupture 

pouring,  chemical  composition,  and  sometimes  even  the  solidity 
cff  sand  and  cores  are  maintained  exactly  constant. 

The  heavy  solid  contraction  of  the  white  cast  iron  also  im- 
poses a  number  of  difficulties  which  would  not  be  clear  to  the 
reader  were  he  to  consider  the  problem  altogether  from  the 
standpoint  of  the  net  shrinkage  of  the  finished  product.  It 
has  been  said  that  the  total  contraction  of  all  white  cast  iron  is 
constant.  However,  it  is  at  least  unusual  that  all  parts  of  a 
given  casting  cool  at  the  same  rate.  In  other  words,  in  prac- 
tically every  casting  some  parts  arrive  at  their  final  temperature, 
and  therefore  final  size,  ahead  of  others.  This  may  develop  ex- 
cessive stresses  or  even  distort  or  disrupt  the  casting. 

Consider  a  casting  having  the  form  of  a  thin  disk  with  a 
heavy  hub  at  the  center,  as  shown  in  Fig.  109.  The  hub  will  be 
hot  and  possibly  almost  fluid  when  the  light  disk  has  already 
set  and  cooled  to  nearly  room  temperature.  The  contraction  of 
the  disk  during  the  cooling  has  met  but  little  resistance  from 
the  hot  plastic  center.  However,  when  the  latter  begins  to  cool 
its  reduction  in  dimensions  will  be  resisted  by  its  attachment  to 

Fig.    110 — Type    of   casting  with   thin   disk   center   and    thick   rim 

Pafternmaking  and  Molding  243 

the  solid  thin  flange.  Sometimes  this  attachment  will  be  so  se- 
cure as  to  permanently  stretch  the  pasty  mass  within.  If  this 
cannot  occur  the  flange  may  be  torn  loose  from  the  hub 
at  one  or  more  places  or  may  even  be  entirely  detached. 

In  the  reverse  case  of  a  thin  plate  surrounded  by  a  thick 
rim,  as  shown  in  Fig.  110,  the  contraction  of  the  rim  would  be 
opposed  by  the  previously  solidified  center,  either  crushing 
the  center  or  producing  a  radial  tear  in  the  rim.  Generally 
the  point  of  failure  is  at  or  near  the  hottest  part  of  the -casting 
Where  the  strength  is  the  least.  Occasionally  no  external  de- 
fect results  due  to  the  welding  up  of  such  defects  by  molten 
metal  from  the  center.  Then  the  consequence  is  a  pipe  or  other 

The  magnitude  of  the  stresses  from  this  source  may  be 
enormous,  depending  only  on  how  rigidly  the  last  cooling  por- 
tions are  held  by  their  solid  surroundings.  In  gray  iron  the 
difficulty  is  less  pronounced  due  to  the  lower  magnitude  of 
the  contraction  and  to  the  fact  that  the  solid  portions  can  be 
deformed  slightly  without  breaking,  whereas  practically  no  dis- 
tortion is  possible  in  the  hard  iron. 

Effect  on  Design  of  Castings 

The  practical  application  of  this  reasoning  is  that,  in  the 
design  of  parts  to  be  made  of  malleable  cast  iron  great  care 
must  be  used  to  avoid  such  forms  and  proportions  as  will  rigidly 
connect  parts  of  widely  different  cross  section.  All  sections 
should  merge  uniformly  into  each  other,  avoiding  abrupt  changes 
of  thickness.  Fairly  thin  ribs  intended  to  rigidly  brace  heavier 
sections,  spoked  wheels  with  hubs  heavier  than  the  rim  and  in 
general  any  design  in  which  unequal  rates  of  cooling  can  set  up 
opposing  stresses  should  be  avoided.  If  such  designs  are  suc- 
cessfully executed  by  the  foundryman  it  is  only  by  methods  'of 
gating  or  chilling  calculated  to  accelerate  the  cooling  of  the 
heavier  sections  and  retard  that  of  the  lighter.  This  calls  for 
the  exercise  of  great  skill  and  judgment  and  may  produce  pro- 
hibitively higher  losses  with  a  corresponding  increase  in  cost. 

We  may  now  consider  the  shrinkage  produced  by  fluid  con- 
traction and  resulting  in  porous  material  in  the  areas  freezing 


American   Malleable    Cast   Iron 

last.  It  is  impossible  to  suppress  these  so  called  shrinks  in  any 
casting.  Their  formation  is  inseparably  connected  with  selective 
freezing  over  a  temperature  interval  and  hence  always  occur  in 
every  casting. 

Depending  on  particular  conditions,  these  shrinks  may  be 
widely  distributed  in  insignificant  amount  at  any  one  place, 
or  they  may  be  concentrated  in  one  spo't,  aggregating  a  consid- 
erable volume.  A  casting  freezing  at  a  nearly  uniform  rate 
throughout,  due  to  equality  of  section,  etc.,  and  freezing  almost 
as  rapidly  as  the  iron  enters  the  mold  may  have  the  porosity 
so  uniformly  distributed  and  so  nearly  filled  up  from  the  ladle 
during  pouring  as  to  be  practically  sound.  On  the  other  hand, 
a  casting  having  a  heavy  cross  section  in  some  one  place  which 

Fig.    Ill — Dendrite    (about  half  size)    from   shrink  in   hard   iron    ingot 

8   inches    in    diameter   by   20   inches    high    which 

was    poured    without    feeding 

is   fluid    long   after   pouring   ceases   will   show   a   great   shrink, 
especially  if  the  heavy  section  is  high  up  in  the  mold. 

Two  remedies  are  employed  for  this  trouble.  The  older  is 
the  application  of  iron  chills,  which  are  pieces  of  cast  iron 
buried  in  the  mold  so  that  they  form  its  inner  surface  at  the 
points  where  shrinkage  is  prevalent.  By  accelerating  freezing 
they  suppress  the  shrink  in  their  immediate  vicinity.  However, 
since  the  reduction  in  volume  still  exists  an  equal  volume  of 
shrinkage  will  develop  elsewhere.  This  practice  is  good  if 
the  shrink  in  the  new  location  does  no  harm,  or  if  in  that  lo- 
cation it  can  be  suppressed  by  feeding ;  otherwise  it  is  merely 
camouflage.  Continuously  supplying  molten  iron  until  the  en- 
tire casting  is  frozen  is  the  only  actual  preventive  of  shrinks. 

Patternmaking  and  Molding  245 

The  shrink  always  is  found  in  the  slowest  freezing  locality. 
Therefore,  if  to  the  pattern  there  is  attached  a  feeder  of  still 
slower  cooling  rate  so  located  that  metal  can  flow  from  it  to 
the  location  in  which  the  shrink  was  found,  then  the  shrink 
will  be  transferred  to  this  feeder  and  be  of  no  consequence, 
since  the  feeder  is  not  a  part  of  the  finished  product.  The 
actual  design  of  feeders,  to  meet  a  given  set  of  conditions  may 
require  much  skill  and  experience,  but  the  operating  principle  is 
simple.  t 

Feeders  are  expensive,  not  only  from  the  molding  view- 
point but  also  because  they  involve  the  melting  of  much  ad- 
ditional iron.  Nevertheless  their  use  is  the  safest  possible  found- 
ry practice  to  insure  sound  castings. 

The  high  freezing  point  of  white  cast  iron  necessitates 
much  greater  care  in  gating  than  is  requisite  for  gray  iron.  The 
relatively  thin  gates  commonly  used  for  that  metal  do  not  admit 
of  a  sufficiently  rapid  flow  to  prevent  freezing  before  the  mold 
is  filled.  Most  castings  must  have  metal  admitted  at  a  number 
of  points  in  order  to  permit  the  mold  to  fill  sufficiently  rapidly. 
Because  of  the  large  gates,  it  is  necessary  to  use  special  means 
to  exclude  slag  or  sand  floating  with  the  current  of  metal.  The 
thin  knife  gates  of  the  gray  iron  industry  will  choke  the  stream 
enough  to  permit  these  impurities  to  rise  to  the  surface  and  be 
trapped  in  the  runners.  The  same  principle  is  used  in  malleable 
foundry  but  greater  care  is  necessary  in  making  the  runners 
large  and  providing  places  for  the  ascending  slag  to  be  trapped 
on  account  of  the  rapid  flow  of  iron  required. 

Frequently  the  iron  is  poured  through  a  strainer  core  placed 
at  the  bottom  of  the  riser,  which  is  intended  to  cause  the  latter 
to  remain  full  of  metal  and  allow  the  slag  to  accumulate  and 
float  up. 

(Because  of  the  quick  filling  of  the  mold,  necessitated  by 
the  quick  freezing  of  the  iron,  great  care  must  be  used  in  se- 
lecting molding  sands,  and  in  venting  the  mold.  The  air  and 
gas  must  be  able  to  escape  rapidly  enough  to  allow  the  iron 
to  enter  at  the  rate  required  to  keep  it  from  freezing  before 
the  mold  is  filled. 

The  selection  of  molding  and  core  sands  of  core  binders, 


American  Malleable   Cast  Iron 

as  well  as  the  actual  ramming  of  the  sand  are  further  influ- 
enced by  the  high  solid  contraction  of  white  cast  iron.  The 
mold  and  cores  must  be  made  so  as  to  give  readily  under  the 
heavy  contraction  of  the  casting  in  freezing.  If  for  instance, 
a  core  be  so  hard  as  not  to  disintegrate  before  the  metal  begins 

Fig.    112— Typical    gate    for    malleable    castings    showing    strainer,    core 

and  skimmer  gates  for  furnishing  clean  metal  for  feeders 

and  producing  sound  castings 

to  shrink  it  may  set  up  such  a  strain  in  the  casting  as  to  actu- 
ally cause  rupture. 

The  patternmaker  can  frequently  save  the  customer  money  by 
a  judicious  selection  of  the  number  of  pieces  made  in  one  mold. 
A  reasonable  increase  in  the  castings  per  mold  is  good  economy. 

f  Any  attempt  to  increase  the  weight  per  mold  by  putting  in 
so  many  pieces  as  to  cause  pouring  difficulties  or  to  prohibitively 
increase  the  dimensions  of  the  mold  it  not  justifiable. 

Patternmaking  and  Molding  247 

In  general  the  steps  in  the  improvement  of  molding  meth- 
ods have  been  as  follows: 

Starting  with  a  plain  pattern  as  the  simplest  equipment, 
the  first  step  was  to  permanently  attach  thereto  models  or  pat- 
terns of  the  gates,  feeders,  etc.,  in  order  that  these  need  not 
be  the  subject  of  separate  operations.  In  the  case  of  small 
parts  this  leads  to  the  mounting  of  several  patterns  on  one  gate. 

To  avoid  the  labor  of  producing  a  parting  by  hand  for  each 
mold,  match  parts  were  introduced,  which  are  merely  a  semi- 
permanent duplicate  of  one  half  of  the  mold  (generally  the 

In  the  interests  of  greater  stability  plate  patterns  were 
developed,  consisting  of  fairly  thin  flat  plates,  usually  of  alumi- 
num with  the  patterns  mounted  on  one  or  both  sides  to- 
gether with  the  gates,  etc.  The  plate  being  at  least  as  large  as 
the  exterior  of  the  flask  separates  the  cope  and  drag  by  its  own 
thickness.  Each  half  of  the  mold  being  rammed  up  off  its 
own  side  of  the  plate,  the  mold  when  closed  corresponds  in  form 
to  the  parts  mounted  on  the  plate. 

To  do  away  with  hand-rapping  the  pattern  to  withdraw  it 
from  the  mold;  air  or  electric  vibrators  often  are  attached.  In 
some  cases,  especially  for  heavy  work,  the  pattern  is  with- 
drawn, usually  by  a  lever  motion,  without  rapping,  through 
a  stripper  plate.  The  stripper  plate  is  merely  a  plate  represent- 
ing the  parting  of  the  mold  having  an  opening  exactly  fitting 
the  contour  of  the  pattern  at  the  parting.  When  drawing  the 
pattern  downward  through  this  plate  the  latter  supports  the 
sand  and  prevents  its  following  the  pattern. 

Unless  the  cope  and  drag  are  duplicates,  two  machines  are 
requisite  for  each  job  as  the  construction  is  evidently  such  as 
to  be  applicable  to  one-half  the  mold  only  for  each  unit. 

Extremely  heavy  work  is  frequently  handled  on  a  roll-over 
machine  which  is  especially  available  for  making  the  drag.  After 
the  drag  is  rammed  up,  necessarily  parting  downward,  the  ma- 
chine facilitates  turning  it  over  to  its  proper  position  by  sustain- 
ing and  counter  balancing  most  of  the  weight  of  the  mold  and 
pattern  by  springs.  The  pattern  is  sometimes  withdrawn 

248  American  Malleable  Cast  Iron 

through  a  stripper  plate  and  sometimes  by  letting  the  mold  sink 
away  from  under  the  pattern  by  a  suitable  lever  motion.  The 
sand  is  compacted  by  hand  ramming,  by  the  use  of  hand  or  air 
operated  squeezers,  and  by  jolt  ramming.  The  latter  operation 
consists  of  mechanically  raising  the  mold  repeatedly  and  allow- 
ing it  to  come  down  on  a  solid  support  which  uses  the  inertin 
of  the  sand  itself  for  compressing  it.  On  floor  work  pneumatic 
rammers  sometimes  are  used. 



OPERATIONS    of    cleaning    and   finishing   malleable    iron 
castings  are  conducted  in  part  by  the  manufacturer,  but 
frequently  also  by  the  consumer.      Some  of  the  simpler 
operations   may   be   dismissed   almost   with   a   word   but   certain 
others  such  as  machining,  welding,  galvanizing,  etc.,  which  are 
performed  usually  after  the  castings  are  delivered  to  the  buyer 
merit  more  extended  discussion. 

Castings  generally  are  cleaned  of  sand  as  the  first  step  on 
leaving  the  foundry.  An  exception  to  this  is  found  in  some 
cases  of  large  muffle  annealed  castings  where  the  finish  is 
relatively  unimportant.  Such  castings  are  often  annealed  with 
out  cleaning.  In  most  cases,  the  hard  iron  castings  are  cleaned 
in  tumbling  barrels,  using  any  of  the  standard  equipment.  The 
operation  is  in  no  sense  distinctive,  the  only  peculiarity  being 
the  brittleness  of  the  castings.  To  avoid  breakage  greater  care 
must  be  used  in  handling  the  material  and  packing  the  barrels 
than  would  be  needed  in  gray  iron  practice. 

Castings  of  a  very  fragile  character  can  not  be  cleaned  in 
this  manner  without  breakage.  Therefore,  it  is  usual  to  pickle 
or  sand  blast  them,  usually  the  former.  Pickling  may  be  in 
dilute  sulphuric  acid  which  loosens  the  sand  largely  by  the  ac- 
tion of  the  hydrogen  gas  formed  on  the  surface  of  the  metal  or 
less  commonly  in  hydrofluoric  acid  which  dissolves  the  silica  sand 
with  but  little  action  on  the  iron.  If  the  latter  acid  is  to  be 
used,  economy  will  dictate  the  mechanical  removal  of  as  much 
sand  as  possible  before  pickling  to  avoid  -the  needless  exhaustion 
of  the  acid  through  the  dissolving  of  loose  sand. 

Castings  Must  Be  Cleaned 

Large  castings  are  sometimes  sand  blasted  one  at  a  time  by 
hand  more  easily  and  safely  than  they  could  be  cleaned  by 
rolling.  A  second  cleaning  is  practically  always  necessary  after 
annealing  and  this  may  be  by  rolling,  often  using  scraps  of 
leather,  old  shoes,  etc.  to  impart  a  polish.  If  clean  cut  edges 


American  Malleable   Cast  Iron 

Fig.  113 — Tumbling  barrels  are  used  for  cleaning  castings 

Cleaning  and  Finishing  251 

are  required,  sand  blasting  is  often  resorted  to  either  in  barrels 
or  by  hand.  Pickling  is  not  common  except  as  a  preliminary 
to  plating.  Sulphuric  acid,  hydrochloric  acid,  and  a  hot  solu- 
tion of  acid  sodium  sulphate  may  be  used  to  remove  the  oxide 
scale  left  by  annealing. 

Since  the  castings  are  very  likely  to  become  warped  during 
the  anneal  a  straightening  operation  is  often  necessary  if  the 
castings  are  at  all  complex  in  shape. 

In  many  cases,  especially  on  complex  and  thin  work,  no 
better  method  can  be  used  than  the  hand  method.  When  pos- 
sible a  drop  hammer  fitted  with  suitable  dies  may  be  employed. 
Since  the  development  of  arc  and  acetylene  welding,  the  practice 
of  reclaiming  defective  material  by  this  process  has  received  at- 
tention both  by  the  producer  and  the  consumer.  The  operation 
of  welding  has  two  entirely  different  aspects,  the  repair  of  me- 
chanically unimportant  faults  of  surface  and  finish  in  the  pro- 
ducer's plant  and  the  repair  of  castings  broken  in  service. 
Reference  will  be  made  later  to  the  latter  process,  that  is  welding 
by  or  for  the  ultimate  consumer.  Limiting  ourselves  for  the 
moment  to  welding  as  practiced  in  the  malleable  foundry,  we  may 
start  with  the  premise  that  the  founder  should  deliver  to  the 
buyer  no  casting  which  is  not  high-grade  malleable  iron  through- 

In  welding,  the  material  of  the  weld  is  melted  and  the  cast- 
ing, in  part  at  least,  is  brought  to  this  same  temperature.  Thus 
in  welding  with  iron,  regardless  of  whether  the  filler  is 
wrought  iron,  soft  gray  iron  or  any  other  material,  the  casting 
will  be  heated  to  a  point  far  above  the  critical  point  and  hence 
on  cooling  will  revert  to  the  condition  of  white  iron..  No  in- 
genuity in  the  selection  of  a  filler  therefore  will  overcome  the 
presence  of  a  glass  hard  spot  at  the  weld.  This  condition  can 
be  obviated  only  by  using  for  a  filler  either  white  cast  iron  or 
malleable,  more  conveniently  the  former,  although  both  will  be 
white  after  remelting.  If  the  welded  casting  is  then  annealed, 
or  re-annealed  precisely  as  in  the  regular  practice  the  material 
in  the  weld  will  be  the  same  as  that  throughout  the  casting. 

The  temperature  of  the  arc  is  so  high  that  a  thin  layer  of 
metal  can  be  melted  and  the  operation  completed  before  the  un- 


American   Malleable    Cast   Iron 

Fig.   114 — Sand  blast  equipment  is  used   for  removing  sand   from  castings 

Fig.    115 — Sorting  and   inspecting   small  castings   are   important   operations 

in  many  plants 

Cleaning  and  Finishing 253 

derlying  metal  is  much  heated.  The  author  once  had  the  op- 
portunity to  observe  the  work  of  an  expert  arc  welder.  Work- 
ing on  castings  retaining  their  original  ferrite  surface,  this  oper- 
ator was  able  to  weld  so  rapidly  using  Swedish  iron  wire,  that  the 
heat  was  confined  to  the  ferrite  layer  and  hence  a  perfectly  soft 
weld  resulted.  Such  a  result  presupposes  two  conditions  not 
usually  existing;  the  first,  the  use  of  an  extremely  skillful 
artisan  and  the  second,  a  character  of  repair  which  does  not  re- 
quire welding  to"  a  part  of  the  casting  below  the  decarburized 
skin;  The  latter  condition,  depending  as  it  does  on  the  char- 
acter of  defect  to  be  repaired,  is  entirely  beyond  control. 

All  Faults  Not  Cured  by  Welding 

Whether  or  not  the  casting  is  annealed  before  welding  has 
no  effect  on  the  final  product  and  may  be  left  to  the  welder's 
discretion.  Welds  made  in  the  above  manner  by  a  skilled  ar- 
tisan will  render  the  product  equal  in  quality  to  an  initially 
perfect  casting.  Since  the  element  of  skill  enters,  however, 
it  may  be  a  measure  of  safety  to  exclude  from  repair  by  welding, 
faults  which  if  not  perfectly  repaired  would  be  the  cause  of 
serious  failures. 

Generally,  snagging  or  the  grinding  away  of  gates,  fins,  etc., 
is  the  duty  of  the  producer.  The  operation  is  performed  either 
with  the  casting  in  the  hard  state  or  after  annealing.  Usually 
most  of  these  imperfections  can  be  broken  off  with  a  light  ham- 
mer before  annealing  and  the  final  finish  produced  by  grinding. 
Grinding  before  annealing  is  slower  and  more  expensive  than 
if  performed  on  the  finished  product.  But  since  the  former 
method  produces  somewhat  better  looking  castings,  especially 
on  sand  blasted  work,  it  is  sometimes  specified  when  the  con- 
sumer feels  that  this  feature  is  worth  the  extra  cost. 

Hard  iron  is  ground  on  a  very  hard  and  rather  fine  grained 
emery  wheel;  malleable  is  ground  on  a  soft  and  coarse  wheel. 
The  size  of  casting  and  finish  required  influence  the  selection 
of  the  exact  grade  of  wheel.  For  malleable  grinding  wheels  of 
artificial  alumina,  14  and  16  grit,  in  a  hard  grade  are  used  ex- 

The  preceding  discussion  covers  the  usual  finishing  opera- 
tions which  the  malleable  foundry  performs  for  its  customers, 

254 American  Malleable   Cast  Iron 

however,  the  customer  may  perform  a  number  of  additional  oper- 
ations. Disk  grinding,  machining,  straightening,  welding,  tin- 
ning, galvanizing,  electro-plating,  occasionally  local  hardening 
and  possibly  other  operations  come  into  this  category.  Since 
the  customer's  requirements  and  method  are  likely  to  be  peculiar 
to  his  individual  conditions,  he  is  better  informed  as  to  his 
processes  than  is  the  manufacturer  of  the  castings.  It  will  be 
well,  therefore,  to  confine  the  present  discussion  to  considera- 
tions of  the  producer's  attitude  toward  these  several  operations. 
Of  the  technique  of  disk  grinding  little  need  be  said,  the 
one  essential  point  to  be  observed  being  that  in  this  as  in  all 
other  forms  of  grinding  the  operation  be  not  crowded  to  the 
point  where  the  temperature  of  the  surface  metal  reaches  Ac^ 
Many  grinding  operations  will  readily  raise  the  metal  in  con- 
tact with  the  wheel  to  a  red  heat.  A  portion  of  a  malleable  cast- 
ing which  has  risen  to  such  a  temperature  has  had  some  of  its 
carbon  recombined  and  has  been  locally  hardened  to  a  degree 
which  may  render  it  brittle  or  unmachinable. 

Should  Allow  for  Finish 

Theoretically,  tool  life  should  be  long  and  cutting 
speeds  high  for  malleable  cast  iron,  since  the  material  be- 
ing cut  is  a  dead  soft  steel  which  is  one  of  the  easiest  ma- 
terials to  machine.  Moreover,  the  presence  of  temper  carbon 
should  favor  machining  both  by  breaking  up  the  chip  and  by 
acting  as  a  lubricant  for  the  chip  and  tool. 

That  this  conclusion  is  correct  is  indicated  by  the  con- 
ditions under  which  malleable  is  machined  in  practice.  In  ma- 
chining malleable  cast  iron  not  much  over  1/16-inch  of  stock  is 
removed  at  one  cut.  Only  in  rare  cases  are  cuts  of  %-inch  to 
5/32-inch  necessary  in  practice.  The  commercial  speeds  in  lathe 
operation  seem  to  run  from  70  up  to  160  or  170  feet  per 
minute.  The  heavier  cuts  usually  are  run  at  the  lower  speeds. 
Fine  feeds  are  commonly  used,  ranging  from  .01  to  .02  inches 
per  revolution.  Although  generally  these  conditions  are  suc- 
cessfully met  in  operation,  machining  troubles  sometimes  are 
encountered.  Therefore  there  is  definite  reason  to  believe,  either 
that  there  exists  a  fairly  wide  range  of  machinability  in  nor- 
mal malleable  or  that  in  individual  cases  an  abnormal  product 

Cleaning  and  Finishing 


is  unexpectedly  encountered  in  a  small  amount  mixed  in  with 
a  large  mass  of  normal  material. 

In  the  absence  of  systematic  study  on  the  point,  no  recom- 
mendations are  possible  by  the  producer.  It  is  well,  however,  to 
point  out  some  special  features  influencing  machining.  If  any  pearl- 
ite  remains  in  the  finished  casting,  it  is  generally  very  near  the  sur- 



Center  of  Rotation 
in  lathe 

-Finish  ed  Diameter 
Original  Diameter- 

Fig.    116 — When   machine    center   and    casting   center    are    not   concentric, 
apparent  hard  spots  may  be  found 

face.  It  is  therefore  well  to  design  malleable  parts  with  a  con- 
siderable amount  of  "finish"  for  it  is  usually  easier  to  remove 
1/16  to  3/32  inches  of  metal  by  turning  or  planing  than  to 
take  a  very  light  cut  which  may  be  almost  entirely  in  this 
slightly  pearlitic  area.  At  the  same  time  this  allowance  is  a 

256  American   Malleable    Cast   Iron 

necessity  to  take  care  of  the  variations  of  expansion  in  annealing 
which  are  not  yet  entirely  under  control  of  the  metallurgist. 

The  film  of  pearlite  just  referred  to  sometimes  gives  the 
misleading  impression  of  hard  spots  in  an  otherwise  sound 
casting.  If  the  finished  surface  is  not  concentric  with  the  sur- 
face of  the  rough  casting  is  may  be  that  in  only  a  few  places 
the  lathe  tool  cut  traverses  the  pearlitic  areas  which  then  act  as 
hard  spots.  The  fact  is  that  this  same  area  of  pearlite  exists 
over  the  entire  surface  and  had  it  not  been  that  the  eccentricity 
in  machining  threw  the  cut  alternately  into  ferrite  and  pearlite, 
no  trouble  would  have  been  encountered. 

Fig.  116  illustrates  this  condition  on  an  exaggerated  scale. 
Such  metal  as  this,  of  course,  is  not  of  the  best  quality;  the 
manufacturer  should  and  does  usually  remove  this  pearlitic  lay- 
er. Howeve'r,  attention  is  called  to  it  here  to  explain  the  cause 
of  complaints  sometimes  made  and  to  suggest  means  of  using 
such  metal  which  is  identical  internally  with  a  normally  an- 
nealed product  when  the  pearlite  is  removed  by  a  cutting  tool. 

Hard  spots  in  malleable,  in  the  sense  of  microscopic  areas 
containing  ungraphitized  carbon,  and  scattered  irregularly 
through  the  mass  of  a  perfect  casting  are  rare  indeed.  So  rare 
is  the  occurrence  that  complaints  of  this  fault  are  found  to  be 
almost  always  based  on  erroneous  observation.  The  symmetri- 
cal pearlite  rim  just  discussed  is  the  most  common  cause  and 
represents  not  a  hard  spot  at  one  or  two  points  but  a  tough 
area  of  little  more  than  microscopic  thickness  parallel  to  the 
surface  throughout. 

Shrunken  Areas  Cause  Trouble 

Occasionally,  also,  a  defective  casting  which  for-  some  rea- 
son has  failed  of  complete  graphitization  is  soft  enough  to 
machine,  though  with  difficulty.  If  after  most  of  the  machining 
is  complete,  a  tool  fails  on  the  casting,  the  machinist  is  apt  to 
feel  that  a  hard  area  has  just  been  encountered.  In  addition 
it  occasionally  happens  that  in  castings  made  without  suitable 
feeder  heads,  a  machining  operation  may  penetrate  a  shrink. 
Such  areas  always  show  a  bright  cut  and  are  mistaken  for  hard 
spots.  Cementite  in  fine  granules  frequently  is  present  in  the 

Cleaning  and  Finishing 


shrunken  areas  and  dulls  the  cutting  tool  if  much  of  the  cut 
is  in  the  shrink. 

If  the  turning  operation  which  penetrates  the  shrink  is 
thread  cutting,  the  threads  will  crumble  away  and  the  metal 
may  be  regarded  as  defective  when  the  fault  is  with  the  feeding 
of  the  individual  casting.  (Both  items  are  to  be  controlled  by 
the  foundry  but  frequently  the  character  of  the  complaint  is 
misleading  as  to  the  cause  of  failure.  In  the  case  of  threading 
and  reaming  operations,  it  is  not  uncommon  to  encounter  diffi- 

Fig.    117 — (left) — Cementite    psrsisting    near    a    shrink.      The    metal    in 

porous    areas    is    somewhat    oxidized.      Fig.    118 — (right) 

Hard  slag  inclusions  just  below  the   surface 

which    may    dull    cutting    tools    rapidly 

culties  with  perfectly  normal  metal.  A  metal  which  has  been 
decarbonized  considerably  may  have  the  entire  thread,  especially 
if  of  fine  pitch,  cut  into  the  pure  ferrite  rim.  Ferrite  cuts 
freely,  but  in  rather  long  chips,  hence  the  flutes  in  dies,  taps 
or  reamers  may  become  clogged  and  prevent  a  clean  cut.  In 
work  of  this  character  too  deep  a  decarbonization  is  objection- 

An  interesting  operation  other  than  machine  tooling  occa- 
sionally may  be  practiced  on  malleable.  This  consists  of  press 
fitting  and  is  accomplished  by  applying  sufficient  pressure  to  a 
casting  to  bring  it  to  the  desired  dimensions  and  perfection  of 
surface.  To  produce  reasonable  perfect  finishes  a  pressure  of 
100,000  pounds  per  square  inch  is  required.  The  method  is 


American   Malleable    Cast   Iron 

Fig.  119 — Malleable  casting  effectively  arc  welded  with  Swedish  iron.  The  changes 
A    is    soft    iron    but   very   slightly   recarburized    from    the    malleable;    B    is    an 

carbon  due  to 

Fig.    120 — Hard    iron    casting    successfully    acetylene    welded    with    hard    iron    and 
slag.     A  is  the  original  casting,  B  the  slag,  C  the  material  of  weld  as  noted 

of   a  little  pearlitc 

Fig.    121— Ineffective    hard    weld    of    malleable    casting    using    ingot    iron    wire   and 
filler   converted  into  hard   iron  by  migration   of    carbon   from   the  malleable. 

bitic  due  to  recombination  of   carbon  at 

Cleaning  and   Finishing 


visible  microscopically  were  insufficient  to  make  notable  difference  in  metal.     Area 
oxide   or    slag   film,    and    C   is    the    malleable    showing   but    little    resolution    of 
close  confinement 

then   annealed.     Note  metallurgical   homogeneity  of   casting  except  for  presence  of 
by   larger   grain    size,    and   D   the   material    of    weld   as    noted   by   persistence 
due  to  decarburization 

acetylene  method.    Neither  material  has  its  original   structure.    A   is  the   soft   iron 
B  is  the  original  malleable  iron,  the  background  of   which  has  become   sor- 
temperature  the  metal  reached  in  welding 

260  American  Malleable   Cast  Iron 

particularly  applicable  where  relatively  small  objects  have  to  be 
brought  to  an  exact  thickness.  It  is  also  possible  to  form 
small  objects,  for  example,  radiator  nipples  in  press  dies.  The 
method  is  sometimes  preferred  where  it  is  desired  to  retain  a 
ferrite  surface. 

Welding  Is  Limited 

Welding  of  broken  or  defective  castings  by  the  user  is  of 
course  subject  to  the  limitations  which  apply  to  this  operation 
when  carried  on  by  the  producer  with  the  additional  difficulty 
that  reannealing  is  impracticable.  Had  the  consumer  facilities 
for  the  long  accurately  controlled  heat  treatments  required,  he 
could  of  course  weld  in  the  same  manner  as  does  the  malleable 
founder.  During  annealing  finished  surfaces  would  suffer  and 
warping  might  possibly  occur.  Under  ordinary  conditions, 
therefore,  welding  with  iron  is  not  to  be  regarded  as  practicable 
as  a  repair  operation.  Thus  no  repair  can  be  made,  irrespective 
of  the  welder's  skill,  which  will  restore  the  original  strength  of 
the  casting. 

The  only  resource  is  to  braze,  that  is,  to  use  bronze  as  the 
welding  material.  The  melting  point  of  bronze  is  low  enough 
to  permit  operating  below  the  critical  point  for  iron  hence 
if  care  is  used  a  weld  can  be  made  without  heating  the  metal 
to  a  dangerous  degree.  This,  however,  involves  great  skill  and 
care  on  the  part  of  the  welder.  Ordinary  brass,  Tobin  bronze 
and  Parsons'  manganese  bronze  has  been  suggested  as  suitable 
for  this  work.  Of  course,  welds  made  with  nonferrous  metals 
do  not  permit  of  the  complete  merging  into  one  another  of  the 
metal  used  as  filler  with  the  material  being  repaired. 

They  apparently  fail  invariably  by  tearing  apart  between 
the  iron  and  bronze,  thus  the  entire  strength  of  either  material 
is  not  developed.  The  strongest  welds  of  this  type  ever  tested 
by  the  writer  were  made  by  an  expert  operator  using  Parsons' 
bronze.  These  welds  developed  an  adhesion  between  iron  and 
bronze  of  substantially  45,000  pounds  per  square  inch  thus 
producing  a  tensile  strength  of  the  welded  part  approximately 
equal  to  the  American  Society  for  Testing  Materials,  specifica- 
tions for  malleable  iron. 

The    failure   occuring   entirely   along   the   plane    of    contact 

'Cleaning  and  Finishing  261 

between  bronze  .  and  iron  produced  a  failure  with  only  a 
negligible  elongation,  as  might  be  expected.  If  the  circumstances 
are  such  as  to  permit  making  a  joint  similar  in  form  to  the 
wiped  lead  joint  of  the  plumber,  running  the  bronze  up  on  the 
side  of  the  iron  part  some  distance  each  way,  welds  occasionally 
can  be  made  with  this  metal  which  develop  the  full  strength  of 
the  original  metal,  elongation  excepted.  Such  welds  are  seldom 
made.  A  manufacturer  of  alternating  current  arc  welding 
equipment  claims  that  with  his  apparatus  and  a  nickel  filler  small 
machineable  welds  can  be  made  in  malleable  cast  iron.  The 
writer  has  not  yet  personally  investigated  this  procedure. 

Work  of  this  character  can  be  intrusted  only  to  very  skillful 
artisans.  Unusual  care  and  ability  are  required  to  produce  me- 
chanically perfect  welds  without  even  momentary  overheating  of 
the  surrounding  metal.  Theoretically,  there  should  be  no  rea- 
son for  preferring  electric  to  acetylene  welding  or  vice  versa, 
T)ut  the  writer's  observation  has  been  that  better  work  is  obtained 
with  the  gas  torch.  Possibly  this  observation  may  be  due  to 
the  relative  skill  of  the  operators  whose  work  has  been  observed. 

Of  straightening  operations  little  can  be  said  here,  since 
these  operations  are  in  general  entirely  mechanical.  Occasionally 
there  comes  to  the  malleable  manufacturer's  attention  heavy 
castings  which  have  been  bent  in  service  and  straightened  in  a 
blacksmith's  fire.  Such  castings  originate  more  particularly  in 
the  repair  shops  of  railroads.  Hot  straightening  is  an  extremely 
dangerous  operation  and  in  general  should  be  avoided  by  the 
consumer  since  even  severe  punishment  under  a  heavy  hammer 
will  do  the  castings  less  permanent  harm  than  an  instantaneous 
heating  above  the  lower  critical  point.  The  best  practice  is  to 
straighten  in  a  screw  or  hydraulic  press. 

Must  Use  Accurate  Temperatures 

Next  to  this  the  use  of  the  lightest  hammer  blows  which 
will  accomplish  the  result  is  to  be  recommended.  Some  castings 
are  of  such  shape  that  nothing  short  of  a  steam  hammer  will 
do  any  good.  In  the  absence  of  properly  fitting  dies  such 
a  hammer  may  so  mar  the  casting  as  to  destroy  its  utility.  Un- 
der these  circumstances  hot  straightening  is  an  advantage  but 
-can  be  executed  only  under  conditions  permitting  of  the  use  of 


American  Malleable   Cast  Iron 

accurately  known  and  controlled  temperatures.  Such  straight- 
ening should  be  done  at  temperatures  between  1000  and  1100 
degrees  Fahr.  At  temperatures  below  900  degrees  Fahr.  the 
metal  is  not  sufficiently  more  ductile  than  when  cold  to  justify 
the  heating  operation  and  at  temperatures  over  1200  degrees, 
the  danger  of  accidentally  overstepping  the  critical  point  is  so 
great  as  to  be  unwarranted.  In  the  absence  of  pyrometer  con- 
trol, hot  straightening  of  castings  whose  failure  would  cause 
loss  of  life  or  heavy  loss  of  property  is  almost  criminal. 

Application  of  protective  coatings  to  malleable  iron  to  in- 
crease its  rust  resistance  yet  remains  for  consideration.  Pro- 
jection is  obtained  by  a  coating  of  metallic  zinc,  applied  molten 

Fig.  122 — Photomicrograph  showing  heavy  pearlitic  rim  which  may  cause 
machining  difficulties 

as  in  hot  dip  galvanizing;  by  a  peculiar  form  of  penetration  at 
temperatures  below  the  melting  point  of  zinc,  as  in  sherardizing ; 
and  by  electroplating  as  in  so-called  electrogalvanizing.  The 
relative  merits  of  the  three  systems  is  so  much  in  controversy 
that  it  is  hardly  within  the  province  of  the  article  to  attempt  any 
decision  as  between  them.  It  is  of  course  essential  to  apply 
such  a  coating  as  will  furnish  the  maximum  protection  under 
service  conditions. 

The  prevalent  opinion  seems  to  be  that  the  results  of  hot 
dipping  are  in  this  respect  superior  to  the  two  competitive 
processes.  On  the  other  hand,  the  author  is  informed  that  a 
large  consumer  of  malleable  in  the  form  of  trolley  parts  after 
exhaustive  tests  determined  to  his  own  satisfaction  the  superi- 
ority of  the  sherardized  coating.  Another  extensive  user  of 

Cleaning  and  Finishing 


malleable,  who  applied  his  own  coating  decided  upon  the  electro- 
plating method  as  being  equally  satisfactory  in  service  and  the 
least  liable  to  injure  the  product  to  be  coated. 

Hot  galvanizing  can  and  should  be  done  without  heating 
the  metal  to  be  coated  above  900  degrees  Fahr.  Under  such 
circumstances  there  is  no  reason  to  fear  any  recombination  of 
the  carbon.  Unfortunately,  however,  there  are  on  record  a 
number  of  well  established  instances  in  which  originally 
perfect  malleable  castings  were  seriously  impaired  by  galvanizing. 

Fig.    123 — (Left) — An   effective   acetylene   weld,    malleable   becoming   sor- 
bitic  due  to  resolution  of  carbon.     A  is  gray  iron  converted  into 
white   cast   iron   by   remelting.     B   is    malleable.    .Fig.    124 — 
(Right) — Tobin  bronze  weld  in  malleable.     Note  absence 
of    oxides   and   slag  in   weld   and   absence    of    recom- 
bination of   carbon  due  to  relatively  low  melting 
point  of  bronze.  A  is  bronze,  B  is  malleable 

Such  castings  are  white  in  fracture  and  quite  brittle.  The  fault  is 
believed  to  arise  from  careless  galvanizing  resulting  in  overheat- 
ing of  the  iron  to  the  point  of  recombination  of  the  carbon.  It 
seems  questionable  whether  a  zinc  bath  could  be  heated  commer- 
cially to  above  Ax.  W.  R.  Bean,  as  a  result  of  extensive  in- 
vestigation, believes  that  such .  recombination  of  carbon  never 
occurs  in  practice.  The  writer,  and  apparently  some  galvanizers, 
feel  that  although  rare,  it  can  not  be  said  that  such  a  recom- 
bination is  commercially  impossible. 

However,  a  very  similar  variation  in  quality  has  been  ob- 

264 American  Malleable   Cast  Iron 

served  where  it  was  positively  determinable  that  no  such  over- 
heating has  occurred.  Indeed,  it  is  sometimes  though  rarely 
observed  in  tinning  where  the  temperature  is  never  too  high. 
The  cause  of  this  well  established  fact  is  still  obscure.  Attempts 
to  correlate  it  with  the  absorption  of  hydrogen  during  pickling, 
with  heat  treatment  alone  and  with  the  action  of  the  zinc  in 
alloying  with  iron  have  all  been  inconclusive.  One  malleable 
metallurgist  in  a  preliminary  private  communication  to  the  au- 
thor expressed  the  belief  that  similar  deterioration  was  caused 
in  steel  and  pure  iron  but  escaped  notice  since  the  difference 
in  the  accompanying  fractures  is  less  visibly  marked  than  in 
malleable  castings. 

Some  experiments  with  various  heat  treatments  at  tempera- 
tures far  below  the  critical  point  would  indicate  the  possibility 
that  the  phenomenon  is  associated  with  the  grain  structure  of 
the  material.  How  these  structural  changes  are  produced  or 
overcome  is  still  entirely  too  little  understood  to  permit  useful 
conclusions  as  to  operating  practice.  It  appears,  however,  that 
these  faults  are  rare  in  sherardized  material  and  have  not  been 
observed  in  the  electric  galvanized  product.  On  the  other  hand, 
hot  galvanizing  is  so  generally  successful  that  it  may  be  con- 
cluded this  operation  is  not  necessarily  harmful  to  the  physical 
properties  of  the  iron.  In  the  absence  of  all  definite  knowledge, 
the  malleable  founder  as  yet  is  unable  to  do  anything  to  assure 
the  success  of  the  operation  nor  can  it  be  said  that  any  one 
grade  of  malleable  is  better  adapted  to  hot  galvanizing  than 

The  difference  in  results  is  more  likely  to  arise  from  vari- 
ations in  the  coating  process  than  from  the  metallurgical  char- 
acteristics of  the  castings.  Most  manufacturers  take  the  ground 
that  they  can  assume  no  responsibility  for  galvanized  material 
beyond  the  delivery  of  acceptable  castings  to  the  galvanizer. 
From  time  to  time  also  tinners  and  galvanizers  think  that  they 
observe  differences  in  the  way  different  lots  of  castings  take  the 
coating.  Occasionally  the  claim  has  been  made  that  entire  ship- 
ments could  not  be  galvanized  or  tinned,  that  is,  that  the  coating 

Cleaning  and  Finishing  265 

could  not  be  made  to  adhere.  No  logical  reason  for  such  a  phe- 
nomenon seemed  evident.  All  malleable  castings  consist  of  the 
same  metallographic  ingredients,  indeed  the  surface  metal  is 
in  all  cases  practically  pure  iron  which  can  be  tinned  or  galvan- 
ized successfully. 

Careful  following  up  of  material  complained  of  for  this 
reason  has  disclosed  that  in  no  case  was  the  fault  with  the  metal 
itself.  Cases  occur  where  the  castings  have  not  been  cleaned 
properly  and  hence  do  not  present  suitable  surface  conditions 
for  coating.  This  is  at  times  the  fault  of  improper  cleaning 
after  annealing  and  also  occasionally  due  to  the  formation  of  a 
rust  or  grease  coating  while  the  castings  are  handled  in 
the  consumer's  plant.  In  some  cases  also  the  fault  has  been 
found  due  to  oxidized  and  dirty  zinc  or  tin  baths  and  to  the  use 
of  tinning  alloys  too  impure  to  give  good  coatings.  A  manufac- 
turer for  "many  years  producing  malleable  castings  which  he 
tinned  himself  in  large  quantities  has  assured  the  writer  that 
no  cases  have  ever  been  found  where  castings  would  not  take 
the  coating  perfectly  if  proper  tinning  practice  is  maintained. 

In  all  that  has  gone  before  in  this  chapter,  great  stress  has 
been  laid  on  the  necessity  of  avoiding  even  momentary  heating 
of  malleable  castings  above  the  critical  point.  If  such  heating 
does  occur  the  carbon  instantaneously  recombines  with  iron  and 
can  be  caused  to  separate  again  only  by  a  slow  cooling  equiva- 
lent to  that  at  completion  of  the  annealing  process. 

In  some  few  cases  advantage  is  taken  of  this  process  to 
reharden  malleable  purposely.  The  combined  carbon  content 
after  reheating  is  a  function  of  the  temperature  attained;  the 
hardness  depends  on  the  cooling  rate  adopted.  The  result  of 
course  is  a  metal  of  entirely  different  character  from  malleable 
iron,  the  malleability  and  ductility  being  entirely  lost  and  a 
new  product  obtained  having  some  of  the  general  characteris- 
tics of  hardened  tool  steel.  Unless  conditions  are  accurately 
controlled,  the  properties  of  the  resulting  metal  may  be  quite 
erratic.  To  the  writer's  knowledge,  the  process  has  not  been 
applied  to  any  important  work.  Case  hardening  is  said  to  have 

266  American  Malleable   Cast  Iron 

been  applied  to  malleable,  particularly  when  used  for  wood 
working  tools,  but  the  author  is  unfamiliar  with  any  such 
practice.  However,  he  has  been  assured  by  a  consumer  that 
quite  recently  at  least  two  producers  still  furnished  castings  for 
edged  tools. 



INSPECTION  and  testing  of  the  finished  product  falls  some- 
what naturally  into  two  subdivisions,  the  examination  of  the 
material  as  to  its  metallurgical  properties,  and  the  inspection 
of   the  individual   castings    for  perfection   of    form,    etc.     The 
first  examination  is  made  generally  on  the'  basis  of  a  system- 
atic control  of  the  works  operations  without  reference  to  any 
particular  castings.     Insofar  as  this  inspection  is  conducted  by 
the  manufacturer  for  his  own  information,  but  one  satisfactory 
system  is  used. 

This  system  consists  as  a  minimum  in  the  chemical 
analysis  of  every  heat,  either  before  or  at  any  rate  promptly 
after  casting  and  the  breaking  in  tension  of  at  least  one  test 
specimen  from  each  heat.  The  chemical  analyses  are  of  no 
interest  to  the  consumer.  The  permanent  recording  of  a  test 
from  each  heat  is  required  by  specification  A47-19,  section  lib, 
of  the  American  Society  for  Testing  Materials. 

The  maintenance  of  a  systematic  record  of  chemical 
analyses  is  an  almost  unavoidable  necessity  to  insure  the  found- 
ryman  against  making  heats  which  will  not  pass  the  specifica- 
tions. Since  test  specimens  will  not  come  through  the  an- 
nealing process  for  10  to  14  days  after  casting,  they  would  not 
give  warning  of  bad  furnace  practice  in  time  to  prevent  the 
manufacture  of  a  considerable  quantity  of  bad  iron.  Some  dif- 
ference of  opinion  may  exist  as  to  just  what  constitutes  ade- 
quate chemical  control  of  the  product,  but  the  greatest  weight 
must  be  laid  of  course  on  the  control  of  those  elements  most 
likely  to  be  subject  to  dangerous  fluctuations. 

Color    Method    Unreliable 

Carbon  and  silicon  certainly  should  be  determined  in  every 
heat.  The  determination  of  manganese  seems  urgent  in  view 
of  the  fact  that  in  air  furnace  practice  this  element  is  oxidized 
in  considerable  amounts.  The  determination  of  these  three  ele- 
ments will  furnish  a  check  on  the  mix,  or  charge,  being  fed  into 


American   Malleable   Cast  Iron 

the  furnaces.  The  fact  that  in  hard  iron  all  the  carbon  should 
be  in  the  combined  state  has  lead  some  chemists  to  the  poor 
practice  of  determining  total  carbon  by  color.  Since  the  ad- 
vent of  the  cheap  and  rapid  direct-combustion  methods  there  re- 
mains no  excuse  for  such  a  practice.  The  color  method  cannot 
be  relied  upon  to  give  correct  values  on  high  carbon  metal  and 
now  survives  mainly  in  consulting  laboratories  doing  cheap 

Fig.    125 — Anatytical   laboratory   in   malleable   plant 

contract  work.  While  occasional  expert  operators  can  consist- 
ently check  the  correct  values  to  perhaps  less  than  0.05  per  cent 
the  author  has  seen  results  emanating  from  supposedly  reputable 
laboratories  as  much  as  0.50  per  cent  in  error.  An  expert 
observer  can  guess  more  closely  by  inspection  of  a  broken 
sprue.  Carbon  values  to  be.  useful  must  be  within  0.05  per 
cent  of  correct  and  should  be  better.  This  is  only  possible  by 
combustion  methods.  Results  by  color  should  be  disregarded  as 

With  good  coal  and  melting  stock,  sulphur  does  not  vary 
much  from  one  heat  to  the  next;  with  poor  fuel,  however,  a 
close  control  must  be  kept.  It  must  be  remembered  that  while 

Inspecting  and  Testing    269 

considerations  of  speed  usually  necessitate  sulphur  being  deter- 
mined by  evolution,  the  results  on  white  cast  iron  seldom  are 
exact  due  to  the  formation  of  compounds  of  carbon,  hydrogen 
and  sulphur.  Oxidation  methods  also  may  fail  due  to  the  evolu- 
tion of  gaseous  sulphur  compounds.  Chrome,  in  the  Aug.  10, 
1921  issue  of  Chemical  and  Metallurgical  Engineering,  presented 
data  on  this  point.  The  writer's  experience  is  that  evolution 
methods  seldom  give  accurate  results  and  may  be  short  25  per 

Fig.    126 — Apparatus    for    determining    carbon 

cent  of  the  total  sulphur.     Oxidation  methods  executed  carefully 
give  the  total  sulphur  but  only  at  the  expense  of  much  time. 

The  phosphorus  content  of  the  metal,  in  a  commercial  sense, 
can  be  predicted  exactly  from  the  analyses  of  the  stock,  there- 
fore the  attention  to  this  element  as  required  by  the  finished 
product  varies  inversely  as  the  supe'rvision  given  the  raw  ma- 
terial. Prudence  will  dictate  the  determination  of  silicon  and 
usually  also  that  of  manganese  at  least  in  every  carload  of  pig 
iron.  The  carbon  content  of  pig  iron  is  fairly  constant  but 
must  not  be  neglected  entirely.  Sulphur  and  phosphorus  being 

270 American  Malleable   Cast  Iron 

subject  to  specifications  should  be  watched  closely.  It  seems 
hardly  necessary  to  describe  in  detail  the  methods  of  iron 
analysis  which  are  applicable  to  hard  and  malleable  iron.  The 
procedure  of  iron  analysis  is  becoming  so  well  standardized 
that  mere  reference  to  accepted  methods  will  doubtless  give 
the  chemist  reader  the  information  he  requires  without  burden- 
ing the  nonchemical  reader  with  uninteresting  data. 

Carbon  should  always  be  determined  by  direct  combustion 
in  oxygen,  determining  the  CO2  formed  either  by  direct  weigh- 
ing in  soda  lime  or  preferably  by  absorption  in  standard 
Ba(OH)2  solution  and  titration  of  the  excess  alkali  with  stand- 
ard HC1. 

Solutions  in  which  1  cubic  centimeter  =^0.10  per  cent  on  a 
1.0000  gram  sample  are  convenient.  It  is  sometimes  an  ad- 
vantage to  add  to  the  sample  about  1  gram  of  carbon-free  iron 
before  burning  to  secure  better  combustion.  The  use  of  CuO 
or  of  platinum  black  to  complete  the  oxidation  is  superfluous. 

Silicon  is  invariably  determined  by  a  modification  of 
Brown's  method  substituting  a  mixture  of  HNO3,  HC1  and 
H2SO4  for  Drown's  method  of  solution.  The  major  precaution 
is  to  bake  well  till  SO3  no  long  comes  off  to  render  SiO2 

For  manganese  the  persulphate  method  of  Walters  is  com- 
mon, finishing  the  determination  either  by  color  or  arsenite  titra- 
tion. It  is  well  to  destroy  "combined  carbon,"  that  is,  the 
colored  nitro  compounds  produced  in  the  reaction  of  cementite, 
with  HNO3  by  oxidation  with  persulphate  before  adding  any 
silver  solution. 

Phosphorus  may  best  be  determined  by  solution  in  HNO3 ; 
oxidation,  in  solution,  with  KMnO4;  precipitation  as  "phospho- 
molybdate";  and  finishing  by  alkali  titration,  all  in  the  usual 
manner.  Where  very  few  determinations  are  to  be  made  direct 
weighing  of  the  "yellow  precipitate"  in  Gooch  crucibles  is  con- 

Evolution  sulphurs  are  made  in  the  usual  way.  Rapid 
solution  in  rather  concentrated  acid  tends  toward  complete 
conversion  of  S  into  H2S.  It  is  also  a  valuable  precaution  to 
heat  the  weighed  sample  for  one  hour  under  graphite  and 

Inspecting  and  Testing  271 

allow  to  cool  slowly  before  dissolving.  The  graphite  must  be 
sulphur  free.  The  writer  prefers  KIo3  to  iodine  as  a  titrating 

If  the  oxidation  method  is  used,  concentrated  acid  and  slow 
.solution  in  a  capacious  and  well  covered  vessel  are  desirable. 
This  should  be  followed  by  evaporation  and  subsequent  bak- 
ing for  one  hour  at  not  over  400  degrees  Fahr.  Precipitation 
is  made  in  a  cold  solution  not  exceeding  100  cubic  centimeters 
in  volume  containing  besides  the  5-gram  sample  6  cubic  centi- 
meters of  concentrated  HC1  using  10  per  cent  BaQ2  solution. 
The  solution  and  filtrate  should  stand  one  or  two  days  to  allow 
the  latter  to  crystallize.  In  view  of  the  length  of  the  process  care 
must  be  used  to  avoid  contamination  by  the  laboratory  atmos- 

Supervise   Sulphur    Content 

Aside  from  economic  considerations  sound  metallurgical 
practice  would  dictate  a  supervision  over  the  sulphur  content  of 
the  fuel.  Taking  into  consideration  the  commercial  variations 
in  fuel,  stock  and  furnace  operations,  a  minimum  standard  for 
good  laboratory  control  will  include  the  determination  of  car- 
bon, silicon  and  manganese  in  each  heat,  silicon  and  manganese 
in  each  car  of  pig  iron,  sulphur  in  all  fuel  taking  an  average 
sample  from  each  group  of  5  to  15  cars  where  coal  is  delivered 
in  large  shipments,  and  occasional  determinations  of  sulphur 
and  phosphorus  in  the  product. 

Extending  the  work  to  include  sulphur  in  each  heat  and 
carload  of  iron,  and  phosphorus  and  carbon  in  each  car  of 
pig  iron  sometimes  may  be  well  repaid.  The  analysis  of  scrap 
material  usually  is  not  of  value  since  no  means  exists  for  ob- 
taining a  true  sample.  Analytical  investigation  of  steel  scrap 
suspected  of  containing  unusual  elements  is  sometimes  justified 
when  buying  scrap  direct  from  the  producer. 

Determination  of  the  tensile  properties  of  one  bar  from 
each  heat  already  has  been  referred  to.  The  best  type  of  works 
control  to  insure  uniformity  of  metallurgical  quality  will  in- 
clude a  permanent  automatic  record  of  all  annealing  oven 
temperatures.  The  progressive  manufacturer  will  further  avail 
himself  of  microscopic  methods  in  seeking  the  cause  for  defec- 


American   Malleable    Cast   Iron 

Fig.  127 — Inverted  types  of  metallographic  microscope 

Fig.    128 — Detail   of    inverted  type   of    metallographic   microscope    (Bausch 

&    Lomb) 

Inspecting  and  Testing  27  Z 

tive  material.  Methods  of  metallography  yield  much  valuable 
information  relative  to  the  cause  of  any  failures  when  these 
are  due  to  mischances  in  heat  treatment. 

The  metallographic  characteristics  of  hard  and  malleable 
iron  already  have  been  discussed  in  connection  with  the  metal- 
lurgy of  the  product.  Extended  discussion  here  would  amount 
to  little  more  than  needless  repetition.  Messrs.  Bean,  Highright- 
er  and  Davenport  presented  in  a  paper  before  the  American 
Foundrymen's  association  in  1920  an  extended  description  of 
"Fractures  of  Microstructures  of  American  Malleable  Cast 
Iron,"  showing  some  40  illustrations  mainly  of  typical  micro- 
structures.  The  interested  metallographer  may  well  consult 
the  original  publication. 

The  technique  of  the  microscopy  of  these  materials  is  in  no 
respect  unusual.  Hard  iron  is  rough  ground  on  an  emery  wheel 
polished  further  upon  fine  emery  cloth  and  finished  upon  broad- 
cloth charged  with  rouge.  Some  operators  conduct  the  inter- 
mediate stages  of  polishing  upon  broadcloth  charged  with  F.  F. 
F.  emery  flour  and  then  upon  broadcloth  and  tripoli.  The  etch- 
ing medium  is  almost  invariably  alcoholic  picric  acid. 

Method  of  Polishing 

In  polishing  malleable  care  is  necessary  to  prevent  undue 
deformation  of  the  soft  material  and  the  "smudging"  of  the 
temper  carbon.  Polishing  speeds  above  600  feet  per  minute 
seem  undesirable.  The  specimen  is  best  flattened  by  milling  or 
planing  followed  by  filing  and  finished  as  previously  indicated. 
Suspended  alumina  has  occasionally  been  used  as  the  polish- 
ing medium. 

The  etching  may  be  with  picric  acid  if  pearlite  is  to  be 
examined  or  usually  better,  especially  if  grain  boundaries  are 
important,  with  10  per  cent  alcoholic  nitric  acid.  A  solution  of 
nitric  acid  in  amyl  alcohol  sometimes  overcomes  a  tendency  to 
stain.  Special  reagents  such  as  alkaline  picrate  or  Stead's  are 
occasionally  required  for  particular  investigations. 

It  is  well  to  begin  the  examination  of  malleable  at  50  or 
100  diameters,  to  obtain  an  idea  of  the  form  and  distribution  of 
temper  carbon  pearlite,  etc.  At  200  diameters  grain  size  can 

274 American  Malleable   Cast  Iron 

conveniently  be  studied.  The  identification  of  solid  solutions 
may  require  500  to  1000  diameters  and  the  finer  details  such'  as 
the  boundary  structures,  minute  residues  of  cementite,  crystals 
of  titanium  cyanonitride  or  nitride  can  be  seen  only  at  1000  to 
2000  diameters. 

From  the  manufacturer's  viewpoint,  inspection  and  control 
of  his  product  in  a  metallurgical  sense  involves  chemical 
analyses  of  raw  materials  and  finished-  castings  to  insure  uni- 
formity of  product,  autographic  pyrometer  records  to  insure  uni- 
formity of  heat  treatment,  systematic  testing  of  tensile  specimens 
to  determine  the  quality  attained  and  metallographic  work  to  seek 
the  cause  of  otherwise  unexplainable  faulty  material.  Inspection 
for  physical  properties  of  the  product  when  conducted  by  or 
for  the  -consumer  best  can  be  made  in  accordance  with  the  Amer- 
ican Society  for  Testing  Materials,  specification  A47-19,  adopted 

„  „    I 


Fig.  129 — A.  S.  T.  M.  Tension  test  specimen 

Sept.  1,  1919.     For  completeness  these  specifications  are  quoted 
in  full  as  follows: 

1 — These  specifications  cover  malleable  castings  for  railroad,  motor 
vehicle,  agricultural  implement,  and  general  machinery  purposes. 


2 — The  castings  shall  be  produced  by  either  the  air-furnace,  open- 
hearth  or  electric-furnace  process. 


3 — The  tension  test  specimens  in  Section  5  shall  conform  to  the 
following  minimum  requirements  as  to  tensile  properties : 

Tensile    strength,    pound    per    square    inch    45,000 

Elongation    in    2-inch,    per    cent    7.5 

A — (a)  All  castings,  if  of  sufficient  size,  shall  have  cast  thereon  test 
lugs  of  a  size  proportional  to  the  thickness  of  the  casting,  but  not  ex- 
ceeding $/&  x  %-inch  in  cross-section.  On  castings  which  are  24  inches  or 
over  in  length,  a  test  lug  shall  be  cast  near  each  end.  These  test  lugs 
shall  be  attached  to  the  casting  at  such  a  point  that  they  will  not  interfere 
with  the  assembling  of  the  castings,  and  may  be  broken  off  by  the  in- 

(b)  If  the  purchaser  or  his  reperesentative  so  desires,  a  casting 
may  be  tested  to  destruction.  Such  a  casting  shall  show  good,  tough 
malleable  iron. 

Inspecting  and  Testing  275 

5 — (a)  Tension  test  specimens  shall  be  of  the  form  and  dimensions 
shown  in  Fig.  129.  Specimens  whose  mean  diameter  at  the  smallest 
section  is  less  than  19/32-inch,  will  not  be  accepted  for  test. 

(b)  A  set  of  three  tension  test  specimens  shall  be  cast  from  each 
melt,  without  chills,  using  heavy  risers  of  sufficient  height  to  secure  sound 
bars.  The  specimens  shall  be  suitably  marked  for  identification  with  the 
melt.  Each  set  of  specimens  so  cast  shall  be  placed  in  some  one  oven 
containing  castings  to  be  annealed. 

6 — (a)  t  After  annealing,  three  tension  test  specimens  shall  be  selected 
by  the  inspector  as  representing  the  castings  in  the  oven  from  which 
these  specimens  are  taken. 

(b)  If  the  first  specimen  conforms  to  the.  specified  requirements, 
or  if,  in  the  event  of  failure  of.  the  first  specimen,  the  second  and  third 
specimens  conform  to  the  requirements,  the  castings  in  that  oven  shall  be 
accepted,  except  that  any  casting  may  be  rejected  if  its  test  lug  shows 
that  it  has  not  been  properly  annealed.  If  either  the  second  or  third 
specimen  fails  to  conform  to  the  requirements  the  contents  of  that 
oven  shall  be  rejected. 

7 — Any  castings  rejected  for  insufficient  annealing  may  be  rean- 
nealed  at  once.  The  reannealed  castings  shall  be  inspected  and  if  the 
remaining  test  lugs  or  castings  broken  as  specimens,  show  the  castings 
to  be  thoroughly  annealed,  they  shall  be  accepted;  if  not,  they  shall  be 
finally  rejected. 


8 — The  castings  shall  conform  substantially  to  the  patterns  or  draw- 
ings furnished  by  the  purchaser,  and  also  to  gages  which  may  be  specified 
in  individual  cases.  The  castings  shall  be  made  in  a  workmanlike  man- 
ner. A  variation  of  ^-inch  per  foot  will  be  permitted. 

9 — The  castings  shall  be  free  from  injurious  defects. 


10 — The  manufacturer's  identification  mark  and  the  pattern  numbers 
assigned  by  the  purchaser  shall  be  cast  on  all  of  sufficient  size,  in  such 
positions  that  they  will  not  interfere  with  the  service  of  the  castings. 


11 — (a)  The  inspector  representing  the  purchaser  shall  have  free 
entry,  at  all  times  while  work  on  the  contract  of  the  purchaser  is  being 
performed,  to  all  parts  of  the  manufacture's  works  which  concern  the 
manufacture  of  the  castings  ordered.  The  manufacturer  shall  afford 
the  inspector,  free  of  cost,  all  reasonable  facilities  to  satisfy  him  that  the 
castings  are  being  furnished  in  accordance  with  these  specifications.  All 
tests  and  inspection  shall  be  made  at  the  place  of  manufacture  prior  to 
shipment,  unless  otherwise  specified,  and  shall  be  so  conducted  as  not  to 
interfere  unnecessarily  with  the  operation  of  the  works. 

(b)  The  manufacturer  shall  be  required  to  keep  a  record  of  each 
melt  from  which  castings  are  produced,  showing  tensile  strength  and 
elongation  of  test  specimens  cast  from  such  melts.  These  records  shall 
be  available  and  shown  to  the  inspector  whenever  required. 

12 — Castings  which  show  injurious  defects  subsequent  to  their  accept- 
ance at  the  manufacturer's  works  may  be  rejected,  and,  if  rejected,  shall 
be  replaced  by  the  manufacturer  free  of  cost  to  the  purchaser. 

These  specifications  contain  a  number  of  points  which 
perhaps  may  be  subject  to  criticism,  nevertheless  representing 

276  American  Malleable   Cast  Iron 

as  they  do  the  consensus  of  opinion  of  a  committee  acting  for 
all  interested  parties  and  having  the  approval  of  a  large  body 
of  able  engineering  specialists,  the  specifications*  may  be  con- 
sidered the  best  practicable  solution  of  the  problem  of  inspec- 
tion of  malleable. 

The  specifications  further  have  the  approval  of  the  Ameri- 
can Foundrymen's  association  and  of  the  American  Malleable 
Castings  association.  Therefore,  it  would  seem  to  the  best  in- 
terests of  all  that  this  specification,  together  with  its  further 
authorized  versions,  should  be  adopted  by  all  producers  and 
consumers  as  a  universal  guide  to  quality.  Any  attempt  to  modi- 
fy or  adapt  it  to  supposed  special  conditions  as  a  rule  will  be 

?  '  " 

o  i  "  *  & 

?  '  " 



£•                         1 








Fig.    130 — Dimensions   of   proposed  tension   test  bar 

productive  of  intolerable  confusion  and  secure  no  compensating 
advantage.  The  benefits  of  standardization  will  be  lost  and  the 
resulting  specification,  not  having  the  foundation  of  mature 
consideration  by  many  minds  is  likely  to  be  less  satisfactory  than 
the  standard.  If  in  any  special  case  it  is  agreed  by  buyer  and 
seller  that  it  is  to  their  mutual  interest  to  waive  the  specifica- 
tions, of  course  no  objections  can  be  made  to  that  course 
provided  the  understanding  is  clear  to  both  parties. 

It  will  be  seen  that  inspection  by  means  of  test  lugs  is  prov- 
ided for  in  the  specification.     This  is  a  valuable  check  on  the 

^Revisions  in  the  specifications  quoted  on  pages  274  and  275  were 
adopted  as  tentative  at  the  1922  meeting  of  the  A.  S.  T.  M.  Section  3, 
is  tentatively  changed  to  read : 

"The  tension  test  specimens  specified  in  section  5  shall  conform  to  the  following 
minimum  requirements  as  to  tensile  properties : 

Tensile    strength,    pounds    per    square    inch 50,000 

Elongation   in   2-inch,   per   cent 10.0 

In  Section  6    (b}.  the  following  sentence  is  added: 

"In  case  one  of  the  retest  specimens  contains  a  flaw  which  results  in  the 
failure  of  the  bar  to  meet  the  specifications,  at  the  discretion  of  the  inspector 
additional  test  specimens  from  the  same  oven  may  be  tested,  or  test  specimens  may 
be  cut  from  castings." 

It  is  further  recommended  that  the  standard  test  specimen  be  modified 
to  conform  to  the  dimensions  shown  in  Fig.  130. 

Inspecting  and  Testing  277 

quality  of  individual  castings.  Test  lugs  are  projections  in  the 
form  of  a  frustum,  of  a  rectangular  pyramid,  or  of  a  cone  which 
are  broken  off  by  the  works  inspector  or  by  the  consumer  to 
determine  the  quality  of  the  metal  in  the  casting.  The  size  of 
these  test  lugs  depends  upon  the  size  and  thickness  of  the  cast- 
ings to  which  they  are  attached.  Thus  it  is  impracticable  to 
lay  down  definite  rules  for  their  size,  form  and  location.  In 
general,  lugs  should  be  applied  to  all  castings  where  quality  is 
important.  Pieces  weighing  less  than  3  pounds  or  heavier  of 
thin  cross  section  are  usually  too  small  to  permit  of  putting  on 
a  lug  and  breaking  it  off  without  damage  to  the  casting. 

The  round  test  lug  is  much  affected  in  appearance  by 
shrinks  and  is  quite  deceptive  at  times.  The  author's  preference 
is  for  rectangular  test  lugs  in  which  the  smaller  dimension  at  the 
point  of  fracture  is  ^4-inch  less  than  the  layer.  Generally  the 
height  of  a  test  lug  should  be  about  equal  to  the  larger  dimen- 
sion at  the  point  of  fracture,  and  the  taper  about  1/32  to 
1/16-inch  per  1  inch  on  each  side. 

Useful  sizes  of  lugs  are  specified  as  follows : 

Dimensions    at  Dimensions 

breaking  point  at  top  Height 

in  inches  in  inches  in 

Class     of     work                    Length    Width  Length   Width    inches 
Very    heavy    sections    1^4 -inch    thick 

and  over    -K            ^  H           Jz  -K 

Intermediate     5/g           ^  -ft           •&  y& 

Light  castings   up   to  ^-inch  thick..     TS           ~fs  Yz           Y$>  .  A 

Test  lugs,  to  represent  the  metal  properly,  must  be  free 
from  shrinks;  hence  in  general  should  be  located  in  the  drag 
of  the  mold.  In  inspecting  castings  by  test  lugs,  care  should 
be  used  that  the  lug  is  not  bent  in  opposite  directions  to  break 
it  off.  The  practice  of  nicking  lugs  with  a  chisel  before  break- 
ing also  interferes  with  a  correct  interpretation  of  the  result. 
Under  such  circumstances  the  lug  breaks  off  "shorter,"  that  is, 
shows  less  toughness  than  it  should. 

Three  factors  must  be  given  consideration  in  determining 
the  quality  of  a  casting  from  test  lug  inspection.  These  items 
are  the  effort  required  to  break  off  the  lug,  the  distortion  it 
sustains  before  breaking,  and  the  appearance  of  the  resulting 


American   Malleable    Cast   Iron 

fracture.  While  the  effort  cannot  be  measured  and  recorded 
in  figures,  after  a  time  it  becomes  simple  to  compare  different 
results  fairly  accurately.  In  general  the  hammer  should  not 
be  so  heavy  as  to  break  off  a  good  lug  with  one  or  two  blows. 
A  fair  idea  of  the  energy  consumed  can  be  formed  from  the 
number  of  blows  required  to  produce  fracture. 

The    amount    of    distortion    in    breaking    usually    increases 
with  the  blows  required  to  do  the  breaking.     Test  lugs  should 

Fig.    131— A    200,000-pound    Olsen    universal    testing    machine 

bend  out  of  line  materially  before  fracture.  All  conditions  be- 
ing equal,  small  test  lugs  will  bend  further  than  large  ones.  On 
small  work  where  small  lugs  may  be  unavoidable,  they  will  often 
hammer  over  flat  before  breaking.  On  heavy  lugs  a  displace- 
ment of  30  degrees  will  indicate  very  good  material.  The  inter- 
mediate and  smaller  sizes  listed  in  the  table  may  bend  some- 
what more,  even  up  to  60  degrees.  Distortion  is  greater  when 
the  break  is  made  by  frequent  light  blows  than  by  a  few  heavy 

Inspecting  and  Testing 


blows.     Striking  the  lug  alternately  on  opposite  sides  of  course 
will  produce  no  distortion  and  hence  is  valueless. 

The  fracture  of  normal  malleable  iron,  in  the  absence  of 
much  compression,  is  of  a  velvety  black  appearance,  having  a 
mouse  gray  rim  of  fair  depth.  Occasionally  two  bands  are  ob- 
served, the  outer  one  being  somewhat  lighter  than  the  inner. 
The  outer  rim  in  such  cases,  however,  is  never  steely  in  ap- 
pearance. In  bending  the  lug  over,  the  concave  side  is  of  course 
considerably  compressed  and  this  compression  so  distorts  the 
crystal  structure  of  the  ferrite  as  to  materially  alter  its  appear- 

Pig.   132 — Ewing-type  extensometer  for  determining  elongation  under  load 

ance.  Toward  the  concave  side  of  such  a  lug  the  fracture  will 
be  silver  white  in  color  and  rather  fine  in  grain,  that  is,  not 
coarsely  crystalline.  This  structure  may  occupy  half  or  even 
more  of  the  entire  fracture.  However,  a  band  free  from  any 
steely  rim  and  of  normal  appearance  will  always  be  found 
toward  the  convex  side. 

.When  the   so-called  "compression   fracture"   is  but   slightly 
developed,  danger  exists  for  mistaking  it  for  a  rim  unless  it  is 


American  Malleable    Cast   Iron 

observed  that  the  white  edge  is  along  one  boundary  of  the  frac- 
ture only  instead. of  uniformly  around  it.  Lugs  broken  by  being 
struck  on  opposite  sides  may  show  this  compression  edge  on  the 
two  opposite  boundaries  and  may  be  difficult  of  interpretation. 
.They  may  even  be  clear  white. 

'-  Occasionally  fractures  are  encountered  which  have  a  so- 
called  "picture  frame"  rim  or  ''shuck."  This  is  a  rim,  usually 
•of  crystalline  appearance,  completely  surrounding  the  fracture  as 

Fig.    133 — Olsen-type.    torsion    testing    machine 

a  band  of  uniform  width.  If  the  rim  is  narrow,  the  material 
may  be  strong  and  will  bend  fairly  well.  Such  rims  usually  con- 
tain pearlite  and  the  resulting  metal  is  not  readily  machinable. 
Where  machining  is  no  object,  a  reasonably  narrow  edge  of  this 
character  need  not  condemn  the  product  if  the  lug  withstood 
punishment  well.  Where  machining  is  involved,  the  inspector 
should  use  discretion  in  taking  any  material  with  edges  in  order 
to  exclude  this  condition. 

Entirely  white  fractures  somewhat  rarely  occur.     These  may 
be  due  to  an  anneal  so  incomplete  that  the  original  hard  iron 

Inspecting  and  Testing 


Fie;.     134 — Leeds    &    Northrup     Co.    apparatus     for    determining     critical 
points    by    Roberts    Austens    method 

structure  is  but  slightly  altered,  in  which  case  the  castings  should 
be  returned  for  reannealing.  Occasionally  the  fracture  is  com- 
posed entirely  of  steely  brilliant  facets  surrounded  by  a  narrow 
rim  of  a  more  gray  color.  Such  iron  is  useless  from  the  Ameri- 
can viewpoint,  being  that  normal  to  white  heart  malleable.  It 
is  due  to  radical  faults  of  chemical  composition  and  cannot  be 
saved  by  any  ordinary  reannealing. 

A    further    type    of    white    fracture    sometimes    met    with 

Fig.   135 — Apparatus   for  measuring  magnetic  properties   of  metal 


American  Malleable    Cast  Iron 

resembles  in  color  and  texture  the  compression  fracture  men- 
tioned before  but  extends  over  the  entire  fracture.  Such  lugs 
usually  bend  but  litlte  though  they  are  decidedly  tougher  than 
those  defective  on  account  of  an  incomplete  anneal.  This  ma- 
terial is  normal  under  the  microscope  and  contains  no  combined 
carbon.  The  fault  lies  with  the  crystalline  structure  of  the  fer- 
rite  and  can  be  remedied  by  suitable  further  heat  treatment. 

A  coarse  black  center  surrounded  by  a  slate-colored  rim 
accompanies  weak  lugs  and  is  characteristic  of  poor,  high  carbon 
material.  Considerable  experience  is  necessary  to  interpret  ab- 
normal fractures  properly.  Indeed,  those  who  pretend  off  hand 
and  from  inspection  alone  to  solve  all  problems  as  to  quality 
of  material  and  causes  of  failure,  usually  overestimate  their  own 

In  many  cases  all  the  resources  of  a  chemical  and  metal  - 
lographic  laboratory  are  required  to  diagnose  troubles.  Since 
the  consumer's  inspector  is  not  interested  in  the  cause  of  trou- 

Fig.  136 — Farmer  fatigue  testing  machine 

Inspecting  and  Testing 


Fig.  1.37 — Charpy  hammer  for  impact  tests 

bles   he   may   be   guided   in   the   acceptance   of   material  by   the 
following   considerations : 

1. — Deformation  of  the  lugs  must  be  up  to  standard. 
2. — Bending  should  require  a  fair  degree  of  effort. 

3. — Irrespective  of  the  fracture,  reject  all  material  in  which 
the  lugs  snap  off  sharply. 

4. — Irrespective  of  a  fracture,  accept  any  material  in 
which  the  lug  has  sustained  much  more  than  average  punish- 
ment as  a  result  of  which  indications  are  rendered  worthless  due 
to  the  heavy  distortion. 

5. — Where  machining  is  to  be  done,  reject  any  castings 
which  have  more  than  a  paper  thin  rim. 

6. — Where  machining  is  no  object,  accept  castings  with  a 
wide  steely  edge  only  if  the  performance  of  'the  lug  under  pun- 
ishment is  unquestionable. 

7. — Reject  all  castings  having  a  coarse  structure  and  the 
slate  colored  rim.  Such  lugs  generally  are  defective  with  respect 
to  the  first  three  tests  also. 

8. — Return  for  annealing  all  condemned  castings  in  which 
the  fracture  is  partially  or  entirely  silver  or  steely  in  color. 


American  Malleable    Cast   Iron 

It  may  be  well  also  for  the  inspector  to  assure  himself  of 
the  absence  of  injurious  shrinkage  by  breaking  hard  or  annealed 
castings  from  time  to  time  and  by  watching  the  fracture  of 
heavy  unannealed  castings  for  the  presence  of  primary  graphite 

f      1 

Fig.    138 — Brinell    hardness    tester 

"mottles."     Both  shrinks  and  mottles  are  found  preferentially  in 
the  last  cooling  sections. 

Occasionally  questions  are  raised  as  to  inspection  for  vari- 
ous purposes  after  arrival  of  the  product  at  the  consumer's  plant. 
Except  in  very  exceptional  cases,  inspection  and  condemnation 
of  entire  lots  on  the  basis  of  faults  observed  on  individual  pieces 
cannot  be  resorted  to  fairly.  As  the  average  malleable  found- 
ry is  operated,  it  is  quite  possible  that  no  two  castings  in  a 

Inspecting  and  Testing  285 

given   sack,   or  barrel,   are   representative   of   the   same  heat   in 
the  melting  department  and  oven  in  annealing. 

The  fact  that  in  an  impartially  drawn  sample  a  certain  small 
number  of  defective  pieces  are,  or  are  not  found  proves  nothing 
as  to  the  remaining  pieces.  Therefore,  only  an  inspection  piece 
by  piece  is  equitable  after  the  castings  can  no  longer  be  identified 
with  certain  specific  lots  made  in  the  foundry.  The  test  lug 
inspection  was  devised  for  this  very  purpose.  Upon  occasion 
the  problem  has  arisen  of  selecting  from  a  large  and  indiscrim- 
inate mass  of  castings  those  too  hard  to  machine. 

Brinell  and  Shore  tests  are  useless  for  the  purpose  unless 
the  material  is  practically  unannealed.  Some  inspectors  feel 
that  the  behavior  under  a  preliminary  drilling  operation  is  suit- 
able as  a  means  of  weeding  out  hard  castings.  Others  have  used 
the  ring  of  the  casting,  that  is,  the  pitch  of  its  musical  note 
when  struck.  However,  none  of  these  methods  are  as  cheap,  as 
simple,  or  as  conclusive  as  the  breaking  of  a  test  lug. 

Occasionally  it  is  desired  to  inspect  the  finished  or  semifin- 
ished article  to  make  sure  of  its  fitness  for  the  intended  loads. 
Where  the  maximum  loads  do  not  require  a  proof  load  beyond 
the  yield  point  of  the  article,  the  application  of  such  a  load  is 
an  ideal  test.  Thus  a  link  belt  can  be  loaded  in  tension  to  about 
the  yield  point  and  defects  which  would  result  in  failure  under- 
service  conditions  can  be  discovered. 

Castings  which  are  straightened  after  a  material  deforma- 
tion receive  of  course  a  test  similar  in  principle  to  such  a  proof 
test.  It  is  therefore  hardly  necessary  to  deal  with  them  here  in 
any  detail.  Inspection  of  castings  as  to  their  being  true  to  size 
and  form,  etc.,  has  not  been  discussed  but  this  is  done  by  the 
usual  methods  of  gaging  and  is  not  different  from  similar  inspec- 
tion on  any  other  product. 



TENSION  is  the  simplest  stress  which  can  be  applied  to  a 
material.  The  ease  of  execution  ,of  this  form  of  loading  has 
made  tensile  tests  a  favorite  means  of  judging  the  quality 
of  a  metal  even  though  relatively  few  structural  details  are  sub- 
jected to  pure  tension  in  service.  When  an  elastic  material  is 
stretched  it  first  lengthens  in  exact  proportion  to  the  applied 
load,  in  other  words,  it  follows  Hook's  law  of  the  proportionalit/ 
of  stress  to  strain.  Beyond  a  certain  definite  loading  the  stretch 
increases  more  rapidly  than  the  applied  load.  The  point  where 
this  occurs,  beyond  which  the  material  no  longer  obeys  Hook's 
law,  is  always  referred  to  as  the  proportional  limit. 

In  many  materials  the  increasing  rate  of  'Stretch  is  at  first 
so  slight  as  to  escape  detection  by  any  but  the  most  sensitive 
of  measuring  instruments.  As  more  and  more  load  is  applied  a 
point  is  usually  readied,  however,  where  the  material  begins  to 
elongate  very  rapidly  with  practically  no  increase  in  the  load 
applied.  This  load  is  called  the  yield  point  and  is  more  easily 
recognized  than  defined.  The  term  elastic  limit,  frequently  used 
and  also  frequently  misused,  signifies  that  stress  up  to  which  the 
material  is  not  permanently  deformed.  In  other  words,  a 
material  may  be  loaded  to  any  amount  up  to,  its  elastic  limit  and 
when  the  load  is  removed  will  return  to  exactly  its  original 
length.  This  test  is  seldom  employed.  Like  the  proportional  limit, 
the  elastic  limit  depends  largely  on  the  sensitiveness  of  the 
available  means  of  measurement. 

Explanation   of  Terms 

Frequently  the  three  points  are  confused  and  used  as  if 
they  were  identical-  The  proportional  limit  is  necessarily  below 
the  yield  point ;  how  much  below  depends  on  the  material 

288 American  Malleable   Cast  Iron 

being  tested  and  the  accuracy  of  the  measurements.  The  elastic 
and  proportional  limits  may  be  considered  identical  in  principle, 
but  up  to  the  yield  point  the  permanent  set,  or  elongation,  might 
be  so  small  as  to  escape  recognition. 

The  reader  should  remember  that  by  the  very  definition  of 
the  proportional  and  elastic  limits  the  apparent  location  of  these 
points  will  vary  with  the  available  methods  of  measurement,  the 
proportional  limit  being  the  largest  load  the  material  will  sustain 
without  visible  departure  from  Hook's  Law,  and  the  elastic 
limit  the  largest  load  it  will  sustain  without  taking  a  permanent 
set.  The  greater  the  precision  of  the  measurement,  the  lower  will 
be  the  stress  corresponding  to  these  definitions.  Doubt  is  fre- 
quently expressed  whether  cast  metals  actually  have  any  propor- 
tional limit  larger  than  zero,  the  thought  being  that  with  suf- 
ficiently delicate  extensometer  measurements,  the  graph  would  be 
a  curve  from  the  origin.  In  view  of  these  facts  an  attempt  to 
find  the  elastic  limit  by  watching  the  drop  of  the  testing  machine 
beam  will  give  apparently  higher  values  than  determining  this 
point  by  the  divider  method  and  the  divider  method  will  give 
materially  higher  results  than  the  extensometer.  The  engineer 
will  therefore  require  to  know  how  these  points  have  been 
determined  in  making  intelligent  use  of  the  information. 

Action  of  Metals  in  Tension 

Most  ductile  materials  when  loaded  in  tension  beyond  the 
yield  point  do  not  stretch  uniformly  at  all  points  of  their  length. 
The  larger  part  of  the  deformation  usually  occurs  quite  close  to 
the  point  of  failure.  The  specimens  accordingly  neck  in  and  finally 
break  at  the  smallest  portion  of  the  necks.  The  per  cent  of  elonga- 
tion is  therefore  less  the  longer  the  gage  length  in  which  it  is  meas- 
ured. The  difference  between  the  area  at  the  point  of  fracture  and 
the  original  cross-sectional  area,  expressed  in  per  cent,  is  called 
the  reduction  in  area.  A  high  reduction  in  area  is  even  more  indi- 
cative of  a  very  ductile  material  than  a  high  elongation.  The  ratio 
of  stress  to  strain,  below  the  proportional  limit,  is  known  as  the 
modulus  of  elasticity-  These  various  constants,  proportional 
limit,  yield  point,  elongation,  reduction  in  area,  modulus  of 
elasticity,  and  ultimate  strength  and  the  relationships  between 
them  give  a  very  good  picture  of  the  behavior  of  any  material 

Tensile  Properties 


under  static  loads.  These  constants  also  yield  some  information 
regarding  its  behavior  under  dynamic  stresses.  The  application 
of  each  constant  is  fairly  evident.  The  proportional  limit  is 
useful  when  the  deflection  must  be  temporary  and  predictable. 
The  yield  point  limits  the  stresses  which  may  be  applied  with- 



b  30000 



Curve  A'  0 
Curve  B-  0 


Diameter   =  0. 
Gage  length*  5 







o.oo  ie 

Unit"     Elongation 

Fig.     139 — Stress-strain    diagram    of    malleable    cast    iron    in    tension 

out  producing  visible  'permanent  changes  of  shape  in  the  mater- 
ial. Elongation  and  reduction  of  area  are  indicative  of  the  amount 
of  distortion  a  material  can  stand  without  fracture.  The  ultimate 
strength  measures  the  load  that  can  be  sustained  without  failure, 
although  with  permanent  deformation.  The  modulus  of  elasticity 
serves  to  determine  the  elastic  deflection  under  relatively  small 
loads.  The  behavior  of  a  material  under  tension  is  most  con- 
veniently expressed  by  means  of  a  stress-strain  diagram,  in 
which  the  elongation  in  per  cent  in  some  definite  gage  length  is 
plotted  against  the  increasing  load  in  pounds  per  square  inch. 
Fig.  139  shows  a  graph  of  this  kind  somewhat  typical  of  malle- 

290 American   Malleable   Cast  Iron 

able  cast  iron.  The  various  constants  are  marked  in  the  graph  in 
the  appropriate  places.  The  curve  is  made  from  a  malleable 
casting  about  the  tensile  strength  .prescribed  by  the  A.  S.  T.  M. 

Malleable  iron  of  higher  tensile  strength  would  have  the 
proportional  limit,  elastic  limit,  and  yield  point  raised  very 
closely  in  the  same  proportion  as  the  tensile  strength  increased.  In 
other  words,  fhe  proportional  limit  would  always  be  about  one- 
third  of  the  ultimate  strength  and  the  yield  point  as  measured 
by  extensometer  about  six-tenths  the  ultimate  strength.  The 
yield  point  determined  by  the  divider  method  will  be  about  two- 
thirds  of  the  ultimate  strength. 

The  tensile  strength  of  malleable  cast  iron,  as  measured  in 
a  test  specimen  of  specified  form  and  dimensions  s'hould  be 
45,000  pounds  per  square  inch  and  its  elongation  in  2  inches 
7l/2  per  cent  according  to  the  1919  specincatioins  of  the  American 
Society  for  Testing  Materials.  The  specimen  is  to  be  of  the 
form  and  dimensions  shown  in  Fig.  129.  The  apparent  tensile 
strength  of  this,  as  of  any  other  cast  product,  is  affected  by  the 
gating  of  the  castings  forming  the  test  specimen.  This  is  not 
due  to  any  effect  on  the  properties  of  the  metal  as  such,  but 
on  the  degree  of  soundness  wlhich  is  secured  in  the  casting. 
Obviously,  to  give  representative  results  it  is  necessary  to  take 
such  precautions  as  may  insure  the  freedom  of  the  specimen 
from  shrinkage. 

Specimens  Must  Be  Representative 

The  point  seems  worthy  of  discussion  in  this  chapter  be- 
cause criticism  and  confusion  often  arise  when  specimens  cut 
from  castings  or  parts  of  castings  do  not  conform  in  properties 
to  the  American  Society  for  Testing  Materials  specimens  from 
the  same  heat.  The  discrepancy  frequently  is  due  mainly  to  inter- 
nal defects  of  the  castings  from  which  specimens  are  taken. 

Failure  of 'such  specimens  to  pass  the  test  indicates  im- 
properly fed  castings  ratiher  than  weak  metal.  The  tensile 
strength  and  elongation  of  malleable  as  made  today  by  the  lead- 
ing manufacturers  exceed  the  American  Society  for  Test- 
ing Materials  specification  by  a  safe  margin,  the  metal  now 

Tensile  Properties 


sold  by  reputable  makers  rarely  being  under  48,000  pounds  per 
square  inch'  in  tensile  strength  and  10  per  cent  in  elongation. 
The  product  probably  averages  about  51,000  pounds  ultimate 
strength  and  12  per  cent  elongation. 

The  tensile  strength  and  elongation  of  daily  specimens 
submitted  by  all  of  the  more  than  60  members  of  the  American 
Malleable  Castings  association  have  been  averaged  by  months 
and  the  results  plotted  as  shown  in  Fig.  140.  The  recent  data 
average  better  than  the  author's  personal  estimate. 

Occasional  record  performances  have  been  noted.  The 
highest  grade  malleable  known  to  the  writer  was  a  single  piece 
having  a  strength  of  58,000  pounds  per  square  inch,  and  an 
elongation  of  34  per  cent.  A  strength  of  64,000  pounds  coupled 
with  an  elongation  of  18  per  cent  was  once  noted.  These  were 
single  isolated  cases  and  in  no  sense  typical  of  a  routine  product. 
One  plant  produced  castings  over  57,000  pounds  ultimate 
strength  and  20  per  cent  elongation  continuously  for  about  a 

As  might  be  expected  from  its  microstructure,  the  tensile 
strength  of  malleable  cast  iron  is  largely  dependent  upon  its 
carbon  content,  since  the  more  carbon  the  greater  the  interrup- 
tion to  the  mechanical  continuity  of  the  casting.  This  applies 
rather  to  the  original  carbon  content  than  to  that  after  anneal. 
Carbon  once  liberated  has  accomplished  its  destruction  of  con- 
tinuity and  even  if  it  can  be  removed  after  formation,  it  leaves 
behind  the  hole  it  occupied. 

Furthermore,  the  other  elements  present  besides  carbon 
may  affect  the  physical  properties  of  the  ferrite  just  as  they  affect 

Fig.    140 — Tensile    strength    and    elongation    plotted    from    specimens 
submitted   by   members    of   American    Malleable 
Castings    Association 

292  American   Malleable   Cast  Iron 

the  properties  of  a  dead  soft  steel.  This,  however,  is  of  less 
practical  importance  than  the  variations  due  to  carbon,  since 
within  'the  limits  capable  of  commercial  annealing  none  of  the 
other  dements  are  likely  to  have  an  effect  of  the  order  of 
magnitude  of  those  due  to  the  latter  element.  The  writer  in  the 
past  has  had  occasion  to  make  comparisons  of  the  tensile  proper- 
ties of  many  thousands  of  'heats  with  their  chemical  composi- 
tions. As  a  rule  investigations  of  this  character  are  influenced  by 
so  many  variables  that  a  summary  which  is  strictly  accurate  as 
well  as  fairly  simple  is  hardly  possible,  save  at  the  expense  of 
space  for  detailed  technical  explanation  which  could  be  spared 
only  in  a  monograph  upon  that  one  subject. 

Increased  Carbon  Lowers  Strength 

In  general  it  may  be  said  that  an  increase  in  carbon  always 
carries  with  it  a  decrease  in  strength  and  elongation.  The  de- 
crease in  strength  per  unit  increase  in  carbon  is  greater  the 
greater  the  total  amount  of  carbon  and  the  higher  the  silicon- 
Manganese  and  sulphur  when  present  in  correct  relative 
proportion  and  within  anything  resembling  commercial  limits 
have  relatively  little  effect.  Phosphorus  up  to  about  0.20  or  0.25 
per  cent  strengthens  the  metal  without  decreasing  its  ductility. 

The  considerations  just /outlined  would  seem  to  furnish  a 
basis  for  a  graphical  or  tabular  summary  of  the  relation  be- 
tween tensile  strength  and  chemical  composition.  The  great  dif- 
ficulty is  that  even  though  the  effect  of  each  element  may  be 
well  established,  there  remain  variables  due  to  the  form  of  test 
specimen,  the  soundness  of  the  specimen  and  the  effect  of  the 
previous  thermal  history  on  the  physical  and  grain  structure  of 
the  ferrite. 

Accordingly  the  presentation  of  such  a  summary  might  be 
misleading  to  the  interested  user  of  malleable  and  would  serve 
:no  useful  purpose  as  a  guide  to  specifications  or  to  successful 
practice,  unless  the  other  variables  could  also  be  successfully 
defined  and  prescribed.  As  a  guide  to  the  general  order  of 
magnitude  of  the  effect  of  carbon  and  silicon  on  normal 
malleable  iron,  Fig.  141  shows  the  average  tensile  strength  of 
malleable  of  varying  carbon  content  but  of  constant  silicon  as 

Tensile  Properties 


averaged  from  a  large  number  of  heats.  An  increase  of  0.01  per 
cent  silicon  decreases  the  tensile  strength  about  20  pounds  per 
square  inch  for  low-carbon  iron  (about  2.25  per  cent),  and 
about  75  pounds  per  square  inch  high-carbon  iron  (about  3.25 
per  cent).  From  these  data  it  would  seem  that  a  simple  arith- 
metical calculation  should  show  what  the  strength  of  malleable 

c  ^nnn 

Per  Cent  C 
235  £.40   £45  £.50   £.55  I. 


DO     U 

>n  Before  Annea 
>5   £70    £.75    £j50  21 


J5  £.90    £.95   3. 


••      * 









i_  A  o  nr\r\ 






















i  = 

,75  PerCer 






Fig.  141 — Effect  of  carbon  on  tensile  properties  of  malleable  iron 

cast  iron  in  pounds  per  square  inch  measured  in  the  American 
Society  for  Testing  Materials  test  specimen  should  be  for  any 
given  composition. 

Any  attempt,  however,  to  apply  these  figures  literally  is 
not  likely  to  be  productive  of  results,  since  the  formula  is  purely 
an  empirical  one  and  since  no  account  is  taken  of  some  of  the 
other  variables,  notably  of  the  effect  of  heat  treatment  in  the 
properties  of  ferrite. 

Malleable  iron,  when  completely  annealed,  stands  alone 
among  the  ferrous  materials  in  that  variations  of  composition 

294  American  Malleable    Cast   Iron 

affect  the  elongation  in  the  same  direction  as  the  strength. 
That  is,  malleable  cast  iron  has  a  higher  elongation  the  greater 
its  strength. 

The  reader  should  not  lose  sight  of  the  fact  that  what  has 
just  been  said  concerning  the  proportionality  of  tensile  strength 
and  elongation  is  only  true  of  completely  graphitized 'products. 

For  many  years  and  up  to  relatively  recently  misguided 
efforts  were  made  by  ill-informed  or  careless  manufacturers 
to  produce  a  metal  of  great  strength  by  using  a  chemical  com- 
position or  heat  treatment  calculated  to  produce  incomplete  de- 
composition of  the  combined  carbon.  The  resulting  metal  is,  of 
course,  stronger  than  good  malleable  cast  iron,  since  the  matrix 
is  more  or  less  pearlitic  instead  of  pure  ferrite;  and  also  since 
less  temper  carbon  is  formed  by  the  amount  remaining  combined 
in  the  matrix.  However,  the  relative  lack  of  ductility  of  the 
pearlite,  interrupted  as  it  is  in  addition  by  temper  carbon,  ac- 
counts for  the  lack  of  elongation  shown  by  material  of  this 
character.  The  elongation  may  fall  as  low  as  2  per  cent  in  such 

High   Strength   May   Be   Deceptive 

Material  in  which  a  strength  approaching  or  exceeding  60,- 
000  pounds  per  square  inch  is  observed,  without  a  correspond- 
ingly good  elongation  (at  least  up  to  the  average  or  preferably 
as  high  as  12  per  cent  or  15  per  cent)  should  be  looked  on  with 
grave  suspicion  as  not  being  the  product  of  well  controlled 
malleable  practice. 

Each  circle  in  Fig.  142  shows  a  group  of  heats  of  a  given 
analysis,  the  different  circles  representing  different  analysis. 
They  are  located  according  to  the  strength  and  elongation  of 
the  resulting  product.  It  is  plainly  evident  that  increasing 
strength  is  accompanied  by  higher  elongation.  This  graph  fur- 
nishes some  basis  for  conclusions  as  to  the  effect  of  chemical 
compositions  on  elongations  by  demonstrating  the  approximate 
proportionality  of  f  the  two  properties.  An  exception  has  been 
noted  in  that  while  silicon  slightly  decreases  tensile  strength 
and  hence  should  decrease  elongation,  the  reverse  is  true  for 
very  low  silicons,  especially  in  the  presence  of  low  carbons.  The 

Tensile  Properties 


departure  may  perhaps  be  explained  in  the  light  of  minor  inter- 
ferences with  complete  graphitization. 

The  tensile  strength  of  malleable  iron   further  varies   with 
the  cross-^sectional  area  of  the  piece  under  ; consideration.   This 
phenomenon  is  not  due  to  the  long-exploded  thought  that  the; 
strength   of    malleable   iron   its   only   in   the  skin.   This  thought 
persisted     from    the     days     when     malleable     iron    was     made; 


.  E  50000 





£  40000 





















>                  7                  6                 9                  10                 II                 \Z 

Elprrcjation  in  2  in  T     percent 

Fig.    142 — Relation   between    tensile    strength   and    elongation    of   mal- 
leable  cast  iron 

"malleable"  by  decarburization  only,  as  is  the  case  with  the  so- 
called  "white  heart"  product  of  Europe. 

The  skin  of  normal  American  or  black  heart  nfalleable  dif- 
fers only  in  degree  from  the  center.  W.  R.  Bean*  gave  figures 
indicating  that  specimens  from  the  same  heats  tested  in  their 
condition  as  cast  and  after  machining  off  at  least  1-16  inch,  and 
sometimes  %  inch  of  the  surface,  had  practically  the  same 
strength.  Tests  made  by  the  writer  indicate  that  on  'sections  'up 
to  one  inch  in  diameter,  after  machining,  the  ultimate  strength 

*Piaper  -presented  at  the  annuad  meeting  of  American   Society  for 
Testing  Materials,   1919. 


American   Malleable    Cast   Iron 

"I  6000 


^  3000 





^  o  -  ro  ^  ^ 

Percent  j 


?.  Data  Plotted  are  the  Difference   - 
v<?w  Constants  for  Rough  Specimens 
1  Constants  for  Turned  Specimens.    — 


















1                           1                            1 

Diameter    as   Tested,  »n. 

Fig.    143 — Comparison    of    tensile    properties    of    machined    and    cast 
specimens  of  equal  diameters 

of  bars  with  the  original  skin  is  about  4000  pounds  per  square 
inch  higher  than  on  bars  from  which  the  skin  has  been  turned. 
The  value  given  varies  with  the  size  of  the  specimen,  as  shown 
graphically  in  Fig.  143. 

The  yield  point  is  not  affected  measurably  by  turning  off 
the  surface.  The  elongation,  however,  is  materially  affected, 
being  decreased  3  or  4  per  cent  by  the  removal  'of  the  surface. 
In  the  case  of  thin  sections,  turning  off  the  surface  reduces  the 
reduction  of  area  5  or  6  per  cent  and  in  extremely  thin  speci- 
mens considerably  more.  It  will  be  seen  that  these  differences, 
although  not  by  any  means  negligble,  are  not  of  an  order  of 
magnitude  to  warrant  the  conclusion  that  the  properties  of  the 
surface  metal  are  all  that  gives  malleable  cast  iron  its  value. 

The  difference  in  unit  strength  between  large  and  small  cross 
sections  may  be  due  to  either  of  three  general  reasons.  The 
large  specimen  may  not  be  so  molded  and  poured  as  to  be  free 
from  shrink.  This  difficulty  usually  can  be  avoided  in  castings  by 
proper  feeders,  unless  the  casting  be  of  especially  intricate  de- 
sign. In  test  specimens  this  remedy  can  always  be  applied  because 
in  this  case  commercial  molding  restrictions  affecting  produc- 
tion never  apply.  Even  when  this  difficulty  is  entirely  overcome 

Tensile  Properties  297 

there  remain  two  other  variables  which  always  prevent  a  large 
section  from  having  the  same  strength  in  pounds  per  square 
inch  possessed  by  a  small  one  of  the  same  metal. 

Both  of  these  variations  arise  from  the  cooling  rate  of  the 
casting.  The  rate  of  cooling  of  the  casting  in  the  molds  affects 
the  final  product  by  its  effect  on  the  formation  of  primary 
graphite  and  by  its  effect  on  the  grain  structure  in  the  hard  iron. 

The  former  difficulty  is  easily  suppressed  by  making  the 
chemical  composition  such  that  no  graphite  will  form  on  freez- 
ing, even  when  the  cooling  is  as  slow  as  any  to  be  expected.  Even 
when  it  is  completely  overcome,  as  is  usually  the  case,  the  effect 
on  grain  structure  persists.  The  size  of  the  ferrite  grains  in 
malleable  in  a  large  measure  is  determined  by  the  graphitizing 
heat  treatment,  although  perhaps  not  to  the  exclusion  of  the 
freezing  conditions.  However  the  size  and  distribution  of  the 
temper  carbon  nodules  is  largely  an  expression  of  the  concensus 
of  fineness  of  the  original  dendritic  structure  of  the  hard  iron. 

Iron  alloys  in  crystallizing  while  freezing  obey  the  same 
laws  as  do  all  other  crystalline  solids  in  that  slowly  growing 
crystals  are  larger  whereas  quickly  formed  crystals  are  small. 
Consequently  a  large  casting  always  has  a  coarser  structure 
than  a  small  one  made  of  the  same  metal  and  to  a  slight  extent 
the  surface  of  any  casting  will  be  of  finer  grain  than  the  center. 

These  differences  are  carried  over  into  the  annealed  product 
since  the  form  and  distribution  of  the  cementite  will  more  or  less 
affect  the  distribution  of  the  ferrite  and  temper  carbon  into 
which  it  breaks  up,  hence  the  quickly  cooled  casting  will  have 
finer  and  more  uniformly  distributed  grains  of  free  carbon  than 
one  cooled  more  slowly.  Fig.  144  shows  the  strength  and  elonga- 
tion of  specimens  varying  in  diameter  from  %  to  1.5  inches. 

A  further  word  of  caution  may  be  necessary.  It  has  just 
been  explained  that  of  the  same  metal  a  small  specimen  is 
stronger  than  a  large  one.  It  is  quite  possible,  at  least  within 
limits,  to  produce  a  metal  of  any  desired  strength  in  any  given 
section  even  if  that  section  be  large.  Thus  castings  having  a 
cross  section  4l/2  x  9  inches  have  been  produced  experimentally 
with  the  material  at  the  center  having  properties  conforming  to 


American  Malleable    Cast  Iron 





?  45  000 




Diameter,  in.,     as   Cast. 

Fig.    144 — Results   of    tests    on    specimens    not   machined 

the  American  Society  for  Testing  Materials  requirements.  Re- 
duction of  airea  is  not  frequently  determined  on  malleable  cast 
iron  since  the  material  is  tested  without  machining.  The  im- 
possibility of  determining  the  area  of  a  comparatively  rough 
specimen  before  testing  precludes  the  determination  of  this 
constant  under  standard  conditions.  Occasionally  the  author  has 
determined  this  constant  for  specimens  ground  truly  cylindrical 
before  annealing.  The  following  table  give's  an  idea  of  w'hat 

.      Tensile  Properties  299 

may  be  expected  when  the  specimens  are  a'bout  ^  inch  in 

Ultimate  strength  in        Per  icemt  of  -elonlgation         Reduction  in  area 

pounds  per  square  indhi  in  2  iniches  in  per  oent 

51,600  21  18 

51,500  20  17 

55,200  19  18 

55,100  13  20 

55,200  17  23 

In  malleable  cast  iron,  as  in  other  materials,  the  reduction  in 
area  decreases  as  the  diameter  of  the  specimen  increases.  It  is 
a  general  principle  that  the  reduction  is  greater  the  fewer  grains 
of  iron  are  contained  in  the  cross  section. 

In  a  certain  series  of  tests  on  a  given  metal  the  following 
results  were  observed: 

Diameter  Reduction    in    area 

indies  per  cent 

*/4  28 

M  20 

*A  18 

M  14 

Castings  Not  in  Tension 

In  engineering  design  malleable  castings  are  seldom  sub- 
jected to  pure  tension.  Loads  in  cross  bending,  compression 
and  in  shear  are  much  more  common.  Indeed,  where  tension  is 
applied  to  malleable  castings  the  load  usually  is  transmitted  to 
the  casting  by  screwing  the  latter  into  a  nut  or  similar  detail. 
Typical  cases  are  malleable  eyebolts  in  turnbuckles.  Although 
the  -shank  of  the  bolt  may  be  in  tension,  consideration  must  also 
be  given  to  the  shearing  strength  of  the  threads  where 
strength  calculations  are  requisite.  Unless  the  design  of 
such  bolt-like  details  is  such  that  the  threaded  end  has 
an  outside  diameter  sufficiently  larger  than  the  shank's  diameter 
so  that  the  area  at  the  root  of  the  thread  exceeds  that  of  the 
cross  section  of  the  cylindrical  body  of  the  bolt  a  further  com- 
plication enters. 

This  complication  is  not  limited  to  malleable  castings,  but 
is  common  to  all  structural  materials.  Nevertheless,  it  is  not 


American   Malleable   Cast   Iron 

infrequently  overlooked.  Tensile  properties  are  measured  on 
test  specimens  usually  cylindrical,  but  at  any  rate  of  as  nearly 
uniform  cross  section  as  can  be  produced.  So  measured,  they  do 
accurately  define  the  material.  However,  if  the  form  of  the 
actual  structural  detail  is  such  that  the  area  of  minimum  cross 
section  is  decidedly  less  than  the  maximum  and  is  localized  in  a 
relatively  short  portion  of  the  axial  length  of  the  detail,  the 

Fig.   145 — V  groove  in  bar 

loading  conditions  are  not  comparable  to  those  obtaining  in  the 
testing  ma/chine. 

Thus  if  a  cylindrical  bar  has  a  sharp  V  groove  turned  into 
it  as  illustrated  in  Fig.  145,  fracture  will  take  place  in  the  area  at 
the  root  of  the  groove.  However,  there  will  be  no  significant 
elongation  of  the  piece  as  a  whole,  for  if  the  total  carrying 
capacity  of  the  section  at  A- A  at  the  smallest  part  of  the 
bar  is  not  such  that  when  distributed  over  the  area 
of  the  body  of  the  bair  at  B,  an  intensity  of  loading 
above  the  yfeld  point  is  obtained,  the  piece  will  tear  apart  at  A-A 
without  any  deformation  to  each  -side  of  the  groove.  Even  if 
the  area  A-A  is  sufficiently  near  that  at  B  so  that  the  body 
is  stressed  beyond  the  yield  point  the  intensity  of  stress  at  B 
must  be  less  than  in  A-A  and  an  inspection  of  the  stress  strain 
diagram  will  show  the  localization  of  stretch  to  be  expected  due 

Tensile  Properties 


to  the  rapid  increase  in  rate  of  deformation  at  the  higher  stress 

Furthermore  the  minimum  area  of  cross  section  apparently 
receives  some  support  from  the  much  larger  areas  immediatel}r 
adjacent.  The  net  result  of  both  phenomena  is  that  a  grooved 
specimen  shows  an  abnormally  low  elongation  and  high  strength, 
as  calculated  on  the  basis  of  the  area  of  fracture. 


Fig.  146 — Necked  specimens  of  pure  iron   (left)   and  malleable   (right) 

This  condition  exists  in  all  bolts  in  which  the  thread  is  not 
cut  on  an  upset  end.  The  magnitude  of  the  departure  from  the 
results  wihich  would  be  expected  from  tension  tests  is  shown  in 
the  following  comparison.  Pairs  of  malleable  test  specimens  of 
the  American  Society  for  Testing  Materials  taken  from  each  of 
six  heats  were  annealed  together.  One  specimen  of  each  pair 
was  broken,  the  other  had  a  sharp  V  thread  turned  into  it,  20 
threads  per  one  inch,  to  produce  a  diameter  at  the  root  of  the 
thread  of  0.505  inch.  These  specimens  were  then  broken,  the 
elongation  being  measured  in  the  threaded  portion  of  the  bar. 

302  American  Malleable    Cast  Iron 

The  standard  specimens  showed  a  tensile  strength  of  52,080 
pounds  per  square  inch  and  an  elongation  of  15  per  cent,  and  the 
threaded  specimens  a  strength  of  60,130  pounds  per  square  inch 
and  an  elongation  of  6^2  per  cent.  Therefore,  in  the  design  of 
threaded  members  a  calculation  based  on  the  normal  ultimate 
strength  distributed  over  the  area  at  the  root  of  a  thread  will 
give  very  safe  results.  Such  threaded  details,  however,  will  not 
elongate  and  inferentially  will  have  their  resistance  to  longitu- 
dinal dynamic  tension  loads  much  reduced. 



COMPRESSION   is   exactly  the  reverse  of   tension  and  is 
a    stress    often    applied    to    malleable   cast   iron.      In   the 
absence   of    free   carbon,   in   products    such   as   steel   and 
wrought   iron,   the   elastic   properties    in   compression   are   very 
nearly  the  same  as  those  in  tension.     In  cast  iron  the  resistance 
to  compression  is  considerably  higher  than  that  to  tension,  as 
may  be  expected  from  the   fact  that  the  graphite  flakes  com- 
pletely enclosed  in  iron  are  less  harmful  under  compression  loads 
than    under   tension. 

Difficulty    With   Ductile  Metals 

Ordinary  cast  iron  specimens  fail  in  compression  by  shatter- 
ing into  fragments,  usually  with  but  little  bulging  at  the 
center.  It  therefore  is  possible  to  determine  definitely  the  ulti- 
mate strength  of  a  given  specimen.  The  ductile  metals,  soft 
steel  for  instance,  are  not  so  definite  in  their  behavior.  Instead 
of  reaching  a  load  where  they  fail  completely  by  shearing  on 
planes  at  45  degrees  to  the  direction  of  applied  stress  or  by 
rupturing  into  fragments  and  ceasing  to  sustain  any  load,  these 
ductile  metals  merely  flow  as  the  load  is  applied  and  never  reach 
a  point  of  complete  rupture.  Thus  a  cylindrical  specimen  of 
steel  takes  a  barrel-shaped  form,  increasing  in  diameter  and  de- 
creasing in  length.  The  increased  diameter  reduces  the  in- 
tensity of  the  applied  stress  and  more  load  therefore  can  be 
applied.  No  actual  point  of  failure  can  be  established,  but  there 
is  a  limit  beyond  which  distortion  of  a  commercial  detail  would 
be  equivalent  to  failure. 

Malleable  least  iron,  being  capable  of  .great  plastic  deforma- 
tion, behaves  in  this  manner  under  compression,  as  indicated  in 
the  two  stress  strain  diagrams  in  Fig.  147.  Curve  B  in  this  dia- 
gram indicates  the  behavior  of  the  same  material  but  not  the 


American   Malleable    Cast   Iron 

same  specimen  from  which  the  diagram,  Fig.  142,  was  charted. 

It  will  be  seen  that  no  definite  point  of  failure  can  be  found 

up  to  a  load  of  90,000  pounds  per  square  inch.     The  permissible 

100  000 


If,  60  000 










Curve  AJ  ( 

Curve  B: 

10000  ^ 




8000    b 




6000  | 





Height:    /" 


'^       o 













y  J 

in.    7 













Area  •, 
Height:  1334  in. 






)                      0.04                   0.08                   0.12                    0.16 
0.0004               0.0006               0.000ft 
—       Unit    Compression.       — 

Fig.   147 — Stress  'Strain  diagram  of  malleable   cast  iron    in   compression. 

The   apparent   deflection    of   0.00043   at   0   load,    Curve   B,   represents   lost 

motion   in    the   machine. 

intensity  of  compressive  stress  depends  therefore  on  the  per- 
manent set  which  can  be  tolerated.  The  graph  readily  permits 
of  the  selection  of  the  load  corresponding  to  any  assumed  con- 
dition of  this  kind.  Note  the  general  similarity  of  the  elastic 
constants  in  tension  and  compression.  The  proportional  limit  is 
15,000  pounds  per  square  inch  in  tension  and  somewhere  above 
13,000  pounds  per  square  inch  in  compression.  The  modulus  of 
elasticity  in  tension  is  25,000,000  pounds  per  square  inch  as 

Compression,  Cross  Bending  and  Shear 


compared  with  22,000,000  pounds  per  square  inch  in  (compres- 
sion. Therefore  the  material  behaves  in  a  manner  very  similar 
to  soft  steel  under  the  two  systems  of  loading. 

Stresses  More   Complex 

The  foregoing  applies  only  to  pure  compression  loads, 
which  exists  only  in  specimens  in  which  the  height  is  not  much 
greater  than  the  diameter.  In  longer  columns  it  is  practically 
impossible  to  keep  the  axis  of  the  specimen  exactly  in  line  with 
the  direction  of  load;  the  column  springs  out  of  line  and  the 
stresses  become  more  complex.  Tests  on  columns  with  fixed 
ends  5/8-inch  in  diameter  and  10.6  inches  high  indicated  that  up 
to  the  proportional  limit  the  modulus  of  elastidty  is  about 


Fig.    148 — Malleable    (center)    and    cast    iron    (right)    in    compression. 

Each  specimen   before  testing  was  of  the  size   and  shape 

shown  at  the  left 

16,000,000  pounds  per  square  inch.  The  fact  that  this  figure  is 
materially  less  than  that  obtained  in  pure  compression  would 
seem  to  indicate  that  even  below  the  proportional  limit  the  stress 
is  not  a  purely  concentric  compressive  one. '  In  this  column  a 
very  definite  failure  at  30,000  pounds  per  square  inch  was  ob- 

Stresses  in  Columns 

The  yield  point  is  quite  definitely  marked  at  25,000  pounds 
per  square  inch.  Insufficient  data  are  at  hand  to  warrant  the 
definite  acceptance  of  any  special  column  formula  for  malleable 
cast  iron.  The  columns  tested  have  a  ratio  of  length  to  diam- 
eter of  about  17  and  therefore  are  more  slender  than  the  average 
column  in  actual  usf  Hence  calculations  based  on  an  ultimate 

306  American   Malleable    Cast   Iron 

strength    of   25,000  pounds   per    square    inch    for   strut   details 
should  be  amply  safe. 

A  well  known  formula  for  cast  iron  columns  with  safety 
factor  of  6  is: 

13,333   x  area   of   column 

Safe  load= 

(column    length)2 

266  x  (diameter  of  column)* 

This  formula  is  equivalent  to  the  statement  that  the  ultimate 
strength  for  cast  iron  columns  is  equal  to 

80,000  pounds  per  square  inch 

i    U*  ' 

1    +    — 

The  ultimate  strength  of  the  malleable  columns  tested  was 
30,000  pounds  per  square  inch,  the  ratio  L/D  being  17.  If  a 
malleable  column  is  subject  to  the  same  general  laws  as  a  gray 
iron  column  then  to  conform  to  the  observed  conditions  the  ulti- 
mate strength  of  a  malleable  column  will  be 
62,000  pounds  per  square  inch 


266  [D 

This  formula  applied  to  the  specimens  tested  in  pure  com- 
pression would  give  a  breaking  load  of  nearly  62,000  pounds  per 
square  inch  at  which  figure  the  material  was  still  carrying  load 
but  had  badly  deformed. 

On  the  basis  of  a  safety  factor  of  6  on  which  the  formulas 
were,  developed  the  safe  crushing  strength  of  malleable  comes 
out  10,300  pounds  per  square  inch,  which  is  well  below  the 
proportional  limit. 

It  is  the  writer's  opinion  that  the  foregoing  formula  can  be 
safely  used  as  a  basis  of  design.  The  safety  factor  could 
probably  be  reduced  readily  to  5  and  possibly  to  4  without 
serious  risk.  For  hollow  cylinders  Kidder  uses  the  value  1-400 
instead  of  1-266  in  the  above  formula;  1-500  for  a  rectangle 
and  1-135  for  an  equal  armed  cross.  In  any  case  D  is  the  least 
diameter  of  the  column  section. 

Compression,   Cross  Bending  and  Shear  307 

When  the  material  is  used  in  the  form  of  a  beam,  it  is  sub- 
ject to  cross  bending  stresses.  This  type  of  loading  is  very 
common  in  practice  and  is  readily  reproduced  in  a  testing 
machine.  The  specifications  of  the  American  Society  for  Test- 
ing Materials  before  1918  and  of  the  United  States  railway 
administration  provided  for  cross  bending  test  results  about 
equivalent  to  a  modulus  of  rupture  or  apparent  maximum  fiber 
stress  of  64,000  pounds  per  square  inch.  This  value  is  decidedly 
too  low  to  correspond  to  the  required  tensile  strength.  The 
modulus  of  rupture  seems  to  be  about  twice  the  ultimate  tensile 
strength  of  the  product,  the  proportional  limit  corresponding 
to  a  fiber  stress  about  equal  to  the  ultimate  strength  in  tension. 
While  not  absolutely  exact  quantitatively,  the  foregoing  state- 
ments do  express  the  general  relationship.  Thus  a  specimen 
cast  from  metal  having  a  tensile  strength  of  about  51,000  pounds 
per  square  inch,  showed  a  proportional  limit  of  50,500  pounds 
per  square  inch,  a  yield  point  of  72,000  pounds  per  square  inch 
and  a  modulus  of  rupture  of  113,000  pounds  per  square  inch. 
The  specimen  was  rectangular  in  cross  section,  ^-inch  deep,  1 
inch  wide  and  12  inches  long  between  supports.  The  constants 
on  specimens  of  different  form  might  be  somewhat  different. 

Stresses  in   Cross  Bending 

It  is  interesting  to  discuss  why  the  modulus  of  rupture  can 
be  higher  than  either  the  tensile  or  compression  strength  of 
the  material.  When  a  specimen  is  bent  there  is  a  tendency  to 
compress  the  material  on  one  side  and  to  stretch  it  on  the  other. 
Somewhere  between  there  is  a  so-called  neutral  axis  where  there 
is  no  change  of  length.  In  material  in  which  the  elastic  be- 
havior in  tension  and  compression  is  the  same  the  neutral  axis 
is  midway  across  the  section.  The  surface  fibers  of  the  speci- 
men are  strained  most  under  such  a  condition,  the  compression 
or  stretch  decreasing  uniformly  as  the  neutral  axis  is  approached. 
As  long  as  the  material  is  perfectly  elastic  the  intensity  of  stress, 
being  proportional  to  intensity  of  strain,  also  varies  uniformly 
each  way  from  the  neutral  axis.  Accordingly  the  material  be- 
haves as  a  perfectly  elastic  body  as  long  as  the  outer  fiber  is  not 
loaded  beyond  the  proportional  limit.  However,  after  that  load- 
ing is  passed  part  of  the  specimen  is  subject  to  plastic  de- 


American  Malleable  Cast  Iron 

Fig.    149 — Diagram    of   stresses    in    cross    bending   of     malleable     iron 

formation.  The  intensity  of  stress  then  no  longer  varies  uni- 
formly from  O  at  the  neutral  axis  to  a  maximum  at  the  top  and 
bottom  of  the  cross-section,  but  there  is  a  band  of  'considerable 
width  next  to  the  upper  and  lower  boundaries  of  the  cross- 
section  in  which  the  stress  is  fairly  uniform.  It  is  only  below 
this  area,  where  the  stress  is  below  the  proportional  limit, 
that  the  uniform  decrease  is  observed. 

The  stress  in  the  outer  fibers  is  then  not  so  great  as  would 
be  calculated,  since  the  permanent  deformation  of  the  specimen 
has  transmitted  some  of  the  stress  from  the  outer  fiber  to  those 
further  in.  Therefore  the  modulus  of  rupture  is  a  purely  the- 
oretical value  not  corresponding  to  any  stress  actually  occurring 
in  the  specimen.  It  is  merely  the  extreme  fiber  stress  which 
would  be  produced  at  the  breaking  load  if  the  material  be- 
haved as  an  elastic  solid  up  to  the  breaking  point. 

In  Fig.  149  the  stresses  in  a  beam  are  indicated  in  diagra- 
inatic  form.  In  a  beam  of  depth  xx;  having  its  neutral  axis  O , 
compression  stress  is  measured  to  the  right  from  xx  and  tension 
to  the  left.  The  proportional  limit  assumed  to  be  the  same 

Compression,  Cross  Bending  and  Shear  309 

under  either  stress  is  shown  by  y  and  3,'.  Loads  which  do  not 
stress  the  beam  above  the  proportional  limit  produce  a  distribii" 
tion  of  stresses  within  the  beam  as  shown  byAOA.  If  the  load 
is  sufficient  to  produce  plastic  deformation  the  stresses  may  be 
as  indicated  by  Bbob'B' ,  which  is  straight  only  between  b  and 
br.  If  OC  is  drawn  so  that  the  area  XOC  equals  the  area 
ObB,  the  C  marks  the  modulus  of  rupture  if  Bbob'B'  corres- 
ponds to  the  load  when  failure  occurs. 

Value  Unexpectedly  High 

In  the  cross-bending  tests  a  load  of  700  pounds  at  the 
center  of  a  12-inch  span  produced  in  a  l/2  x  1-inch  beam  a  de- 
flection of  0.076  inch  at  the  proportional  limit.  Up  to  this 
point  the  deflection  of  the  beam  has  been  elastic,  hence  tlie 
value  of  the  modulus  of  elasticity  can  be  readily  calculated. 

Letting  W  be  the  load  =  700  pounds 
X  —  deflection  at  center  =  .076  inches 

L  =  span  of  beam  =      12  inches 

b    =  width  of  beam  =      1  inch 

d    =  depth  of  beam  =      ^  inch 
W  L3 

E= —    — =31,800,000-{-pounds  per  square  inch 

The  value  is  unexpectedly  high  both  as  compared  with  fig- 
ures for  the  tension  and  compression  experiments,  and  as  com- 
pared with  the  value  for  steel,  which  is  about  29,000,000  pounds 
per  square  inch.  It  is  barely  possible  that  the  error  is  due 
to  slight  errors  in  the  uniformity  of  d  in  the  above  formula. 
Furthermore  the  proportional  limit  and  cognate  elastic  constants 
are .  necessarily  somewhat  obscured  in  a  beam  specimen  owing 
to  the  fact  that  a  relatively  small  portion  only  of  the  beam  is 
subjected  to  maximum  stress.  Only  metal  near  the  surface  and 
in  the  plane  of  maximum  bending  moment  actually  is  sub- 
jected to  maximum  strain,  hence  the  observations  are  largely 
influenced  by  the  behavior  of  the  much  larger  mass  of  metal 
subjected  to  a  much  lower  intensity  of  stress.  It  is  probable 
therefore  that  the  elastic  constants  will  be  apparently  too  high 
in  specimens  of.  such  form  that  a  considerable  amount  of  material 
is  located  close  to  the  neutral  axis.  The  departure  of  the  ap- 
parent elastic  properties  in  cross  bending  from  those  determined 

310  American   Malleable   Cast  Iron 

in  tension  will  be  greater  the  greater  the  ratio  of  the  area  of 
cross  section  of  the  beam  to  its  moment  of  inertia  of  that  area 
about  the  neutral  axis.  For  purposes  of  calculation  a  conserva- 
tive value  probably  would  be  below  29,000,000  and  possibly  as 
low  as  25,000,000  pounds  per  square  inch  to  conform  to  the 
tensile  results  for  the  modulus  of  elasticity. 

Shear  and  Torsion 

Shear  and  torsion  are  the  two  remaining  static  stresses  to 
be  considered.     They  are  closely  related  with  one  another  and 

Disp/Qcemenf  of  P/anes 
by  Tors/onal  Shear. 

D/'sp/Qcemeni-  of  P/anes 
by  L/near   Shear 

Fig.    150 — Displacement  of   planes    by   linear   shear   and    (at  right)    by 

torsional   shear 

involve  the  sliding  of  the  metal  on  itself,  the  slip  taking  place 
along  a  series  of  planes  within  the  material.  Shear  involves  a 
linear  diplacement,  while  in  torsion  the  displacement  is  angu- 
lar. Rivets,  bolts  or  pins  are  subject  to  shear  when  an  attempt 
is  made  to  slide  the  parts  they  hold  together  in  a  direction  at 
right  angles  to  the  axis  of  the  pin.  It  also  is  the  shearing 
strength  of  a  material  which  resists  the  punching  or  cutting 
in  a  die  in  a  pun'ch  press.  A  knowledge  of  the  shearing  strength 
of  malleable  therefore  is  important  both  in  the  design  of  the 
shackle  pins  and  similar  details  and  in  the  selection  of  punch 
presses  to  be  used  in  fabricating  the  product.  Determinations 
made  by  driving  a  punch  of  known  diameter  through  a  plate 
of  known  thickness  and  measuring  the  force  exerted  in  a  testing 

Compression,   Cross  Bending  and  Shear 


machine  have  shown  the  shearing  strength  of  malleable  to  be 
about  45,000  pounds  per  square  inch.  Similar  experiments  made 
by  shearing  off  a  cylindrical  pin  (double  shear)  gave  values  on 
the  same  metal  of  a  little  more  than  41,000  pounds  per  square 


Yield  Point 

Proportional   Limit 
14000  Ib.persq.  in. 


Diameter  —--O."90 
Gage  Length— 5" 


0.004-         0.006          O.OOS          0.010          0.012          0.014 
Unit  Shearing   Strain  in  Extreme  Fiber. 

Fig.    151 — Stress    strain    diagram    of    malleable    cast    iron    in    torsion 

inch.  The  first  mentioned  experiments  probably  are  the  more 
trustworthy.  The  experiments  were  made  on  metal  having  a 
probable  tensile  strength  of  50,000  to  52,000  pounds  per  square 
inch.  Therefore  the  shearing  strength  apparently  is  about  15  or 
20  per  cent  less  than  the  tensile  strength  of  the  product. 

In  the  case  of  elements  in  a  design  subject  to  twisting  loads 
there  is  a  tendency  to  shear — not  by  a  sliding  motion  of  the 
planes  within  a  solid — but  by  a  rotating  a'ction,  one  plane  over 


American  Malleable   Cast  Iron 

another  as  shown  in  Fig.  150.  Evidently  the  action  is  of  exactly 
the  same  character  in  both  cases.  A  twisting  load  is  measured 
by  the  product  of  the  force  applied  and  its  distance  from  the 
axis  of  rotation.  This  product  is  called  the  moment  -of  the 
force  about  the  axis  of  rotation,  or  more  briefly  the  torque,  and 
is  measured  usually  in  inch  pounds.  An  inch  pound  is  the 
moment  of  a  force  of  one  pound  applied  one  inch  from  the 

Fig.    152 — Diagram   showing   factors    to   be    considered   in   determining 

torsion    stresses 

axis  of  the  specimen.  When  a  shaft  is  twisted  the  metal  is 
evidently  deformed  or  strained  more  at  the  surface  than  at  the 
center,  the  strain  being  proportional  to  the  distance  from  the 
axis.  As  long  as  the  metal  obeys  Hook's  law  of  the  propor- 
tionality of  stress  to  strain — that  is,  as  long  as  it  is  not  stressed 
beyond  the  proportional  limit — the  stress  also  is  proportional  to 
the  distance  from  the  tenter  and  mathematical  analysis  will  de- 
fine the  moment  of  torsional  resistance  of  a  section  of  given 
geometric  form  in  terms  of  the  dimensions  of  the  cross  section 
and  of  the  shearing  stress  in  the  outside  fiber. 

The  condition  is  similar  in  character  to  that  existing  under 
cross-bending  stresses.  When  the  intensity  of  stress  in  the 
outside  fiber  passes  the  proportional  limit  a  mathematical  analysis 
of  the  load  condition  is  no  longer  possible,  since  the  distribu- 

Compression,   Cross  Bending  and  Shear  313 

tion  of  stress  is  no  longer  proportional  to  the  distribution  of 
strain.  The  modulus  of  rupture  in  shear  or  the  apparent  stress 
in  the  extreme  fiber  when  breaking  occurs  is  higher  than  the 
true  value,  since  these  layers  stressed  above  the  proportional 
limit  carry  a  stress  more  nearly  equal  than  their  distance  from 
the  axis  of  rotation  would  indicate. 

Fig.  151  shows  a  stress  strain  diagram  of  the  behavior  of  the 
material  in  torsion.  The  load  is  recorded  in  terms  of  intensity 
of  shearing  stress  in  pounds  per  square  inch.  This  is  calculated 
from  the  known  dimensions  of  the  specimen  and  the  measured 
torque.  The  intensity  of  shearing  strain  is  determined  in  terms 
of  the  ratio  of  the  linear  displacement  of  a  point  on  the  surface 
to  the  gage  length.  If  within  a  gage  length  of  5  inches  a  given 
load  has  produced  a  twist  such  that  a  point  on  the  surface  has 
advanced  .07  inch  the  shearing  strain  is  .07/5=.014.  In  other 
words,  the  intensity  of  shearing  strain  is  measured  by  the  tangent 
of  the  angle  *  through  which  an  originally  straight  element  of 
the  cylindrical  surface  is  displaced.  Thus  in  Fig.  151,  if  W  is  the 
load  and  D  its  distance  from  the  center,  the  torque  is  WB. 
S  is  the  stress  in  the  outer  fiber,  L  the  gage  length  of  the 
specimen,  F  in  linear  measure  is  the  displacement  of  the  point 
by  twisting  under  the  torque  WD  from  its  original  position,  A 
to  A'.  The  intensity  of  the  shearing  strain  is  F/L,  the  value  of  F 
being  determined  from  the  known  radius  of  the  specimen  R 
and  the  angle  e,  through  which  one  end  of  the  gage  length 
has  been  twisted  with  respe'ct  to  the  other. 


e  (in  radians)  being  —  • 

if  e  is  in  degrees.  The  value  of  S  is  computed  from  the  couple 
WD  and  the  moment  of  inertia  of  the  circle  of  radius  R  about 
its  center  on  the  supposition  that  the  stress  increases  uniformly 
from  the  center  to  circumference, 

this  giving  S==  --  . 


It  will  be  seen  from  Fig.  151  that  the  proportional  limits  and 

314 American   Malleable   Cast  Iron 

yield  points  are  not  very  different  from  those  in  tension  and 
compression.  The  shearing  modulus  of  elasticity,  however,  is 
not  the  same  as  Young's  modulus.  The  course  of  the  curve 
during  plastic  deformation  is  riot  very  instructive,  since  it  is 
considerably  influenced  by  the  testing  speed.  The  preceding  dis- 
cussion summarizes  the  available  information  with  regard  to 
the  resistance  of  malleable  cast  iron  to  the  various  well  known 
forms  of  static  loading. 



THUS  far  only  static  loads  have  been  considered  in  the 
discussion  of  the  mechanical  properties  of  malleable  cast 
iron.  There  are  many  industrial  applications  of  castings 
in  which  the  structural  detail,  instead  of  merely  sustaining  a 
steady  load  of  some  specific  character,  is  subjected  to  blows, 
shock,  or  repeated  reversals  of  the  applied  stress.  Unfortunate- 
ly, our  knowledge  of  the  principles  underlying  the  behavior  of  a 
material  under  dynamic  stress  still  is  imperfect.  A  great  deal 
of  experimental  work  of  this  character  has  been  done  and  the 
results  published  but  no  method  is  as  yet  available  for  systema- 
tically correlating  the  data  and  deriving  general  principles. 

In  general  the  energy  of  rupture  of  a  given  specimen  and 
material  can  be  calculated  from  its  stress  strain  diagram,  the 
area  below  the  graph  representing  the  product  of  stress  and 
strain  measuring  the  energy,  in  foot  pounds,  for  example.  The 
specimen  may  absorb  this  amount  of  kinetic  energy  from  an  im- 
pact or  other  dynamic  stress.  This  however,  does  not  tell  the 
entire  story  for  the  possibility  of  a  time  factor  enters.  Assume 
that  the  impact  is  due  to  a  weight  moving  with  a  given  velocity. 
The  specimen  absorbs  energy  from  the  weight  by  retarding,  and 
ultimately  stopping  its  motion.  Energy  is  measured  as  a  prod- 
uct of  mass  and  therefore  acceleration  in  the  energy  absorbed 
by  the  specimen  is  measured  by  the  product  of  the  mass  of 
the  weight  and  its  (negative)  acceleration  when  being  stopped 
by  the  weight.  If  we  have  means  of  knowing  the  maximum 
rate  of  retardation  while  the  weight  is  being  stopped,  we 


can  calculate   the   maximum   stress   as   being  —   and   where   M 


is  the  mass  of  the  hammer;  A,  its  maximum  retardation  and 
G,  the  acceleration  due  to  gravity.  Obviously  this  value  cannot 
be  greater  than  the  ultimate  strength  of  the  specimen  without 
producing  failure. 

316 American  Malleable  Cast  Iron 

Dynamic   Stresses  in    Two    Groups 

Two  groups  of  dynamic  stresses  may  be  recognized. 
One  of  these  results  from  impact  or  blows.'  In  general  such 
stresses  are  in  one  direction  only  and  usually  are  of  considerable 
intensity.  They  may  be  applied  axially,  either  in  tension  or  com- 
pression to  'the  detail  involved,  or  may  be  applied  to  a  cantilever 
beam  or  to  one  supported  at  both  ends.  Occasionally  the  load- 
ing is  even  more  complex. 

The  other  group  of  stresses  results  from  repeated,  usually 
rapid,  reversals  of  stress,  sometimes  of  small  magnitude,  and 
usually  through  an  extended  period  of  time.  The  stresses  in  a 
rotating  shaft  acting  also  as  a  beam  are  of  this  character,  as 
are  also  the  stresses  in  the  leaves  of  an  automobile  spring, 
those  in  the  couplers  of  a  train  while  in  motion,  and  those 
resulting  from  vibration. 

In  the  former  group  a  mathematical  analysis  of  the  service 
conditions  is  almost  impossible.  The  material  usually  is  stressed 
beyond  its  elastic  limit  by  each  blow  so  that  it  is  impossible 
to  determine  the  stress  distribution  within  the  metal.  The  energy 
absorbed  by  a  given  specimen  before  breaking  is  frequently 
less  if  the  energy  be  delivered  by  a  single  impact  than  if  deliv- 
ered by  a  series  of  equal  smaller  impacts  whose 
sum  is  equal  to  the  energy  of  the  single  impact  required 
for  fracture.  If  fracture  takes  place  under  a  series  of 
blows  the  energy  absorbed  depends  on  whether  the  successive 
blows  are  of  the  same  intensity  or  increase  in  intensity  with 
each  succeeding  blow.  The  subject  will  be  discussed  more  fully 
in  the  next  chapter. 

Thus  it  is  seen  that  practically  no  two  cases  are  alike 
in  practice  and  that  the  problem  is  so  complex  as  to  prevent 
generalization  from  the  results  of  different  groups  of  tests  by 
mathematical  analysis. 

Therefore  it  is  impossible  to  furnish  quantitative  data 
to  be  used  as  a  basis  of  computation  for  mechanical  details 
subject  .to  impact. 

The  comparison  of  the  behavior  of  several  materials  under 
impact  is  easier  since  the  tests  of  all  can  be  made  under  the 
same  circumstances  and  on  geometrically  similar  specimens. 

Fatigue,  Impact  Hardness  and  Wear 317 

To  avoid  the  complication  resulting  from  -the  cumulative  effect 
of  repeated  stresses  each  insufficient  to  produce  failure,  the 
experiment  usually  is  designed  to  break  the  specimen  at  the 
first  blow  and  to  measure  the  energy  absorbed  in  breaking  by 
taking  the  difference  in  -the  kinetic  energy  of  the  system  be- 
fore and  after  failure.  The  tests  so  made  on  various  types 
of  machines  do  not  give  comparable  data;  the  results  differ 
with  the  design  of  the  hammer,  the  shape  of  the  specimen 
and  its  manner  of  support. 

It  is  said  that  on  the  Charpy  machine,  which  takes  a  speci- 
men 10  millimeters  square  by  53.3  millimeters  long,  with  a 
45-degree  V  notch  3  millimeters  deep  at  the  center,  about  7l/2 
foot  pounds  are  absorbed  in  breaking  a  specimen  of  normal 
malleable  cast  iron.  On  similar  specimens  except  that  the  notch 
is  made  by  a  thin  saw  cut  running  into  a  hole  1  millimeter  in 
diameter,  7l/2  to  8^2  foot  pounds  of  energy  usually  produce 
rupture  in  tests  in  the  author's  laboratory.  On  the  Olsen  ma- 
chine breaking  a  round  cantilever  specimen  with  a  45-degree  V 
notch  0.122  inch  deep  1.10  inches  from  one  end  and  with  the 
notch  clamped  even  with  the  vice  jaws  holding  the  specimen  and 
the  hammer  striking  0.625  inch  above  the  notch,  the  indicated 
energy  absorption  in  breaking  is  13  foot  pounds. 

Testing  Tensile  Impact  Stresses 

Impact  tests  may  also  be  made  in  tension-  In  such  cases 
the  test  is  made  on  a  screw-end  tensile  piece,  one  end  of  which 
screws  into  the  hammer  of  the  Oharpy  machine.  The  other  end 
of  the  specimen  carries  a  yoke  which  strikes  a  fixed  portion  of 
the  frame  of  the  machine  just  as  the  hammer  is  at  the  lowest 
point  of  its  travel.  The  dimensions  are  so  chosen  that  the 
energy  of  the  hammer  is  sufficient  to  rupture  the  piece. 

Evidently,  for  a  given  material  the  energy  to  produce 
rupture  varies  as  the  cross  sectional  area  and  as  the  length 
of  the  specimen.  Upon  the  area  depends  the  resistance  of  the 
material  to  tensile  loads,  and  the  length  is  a  factor,  since  ob- 
viously twice  as  much  work  is  done  in  stretching  a  piece  two 
inches  long  a  given  percentage  of  its  length  as  in  stretching  a 
piece  one  inch  long  an  equal  percentage. 

318 American   Malleable   Cast   Iron 

Speaking  more  technically,  the  expression  for  work  is 
fs  where  /  is  the  force  exerted  and  .?  is  'the  distance  through 
which  the  hammer  moves  while  the  specimen  is  breaking.  If 
a  is  the  area  of  the  specimen,  E  its  elongation  and  /  its 
length,  and  if  t  is  its  ultimate  tensile  strength: 

f  =  Kta 
s  =  El 

fs  =  Kta   El  =  KtEv 

where  K  is  a  constant  depending  upon  the  form  of  the  stress 
strain  diagram  and  v  the  volume  of  the  specimen  equal  to  a  I. 
The  resistance  to  tensile  impact  is  thus  to  be  expressed 
not  in  pounds  per  square  inch  of  section  but  in  foot  pounds 
per  cubic  inch  of  metal  deformed. 

It  is  noteworthy  that  while  in  static  tension  a  defect  op- 
erates to  reduce  the  strength  rather  less  than  in  proportion 
to  its  area  and  the  elongation  considerably,  in  dynamic  test- 
ing practically  absolute  soundness  of  specimen  is  required.  If 
a  notch  or  shrink  exists  sufficiently  large  to  so  far  reduce 
the  area  as  to  localize  the  stretch  wiithiii  its  own  length  the 
gage  length  upon  which  the  work  is  expended  becomes  only 
the  axial  length  of  the  shrink.  This  may  be  only  10  per  cent  or 
even  only  1  per  cent  -of  the  apparent  gage  length  and  the  foot 
pounds  absorbed  if  calculated  on  the  intended  gage  length 
would  be  only  10  or  1  per  cent,  respectively,  of  the  correct 
values.  Care  must  further  be  used  to  see  that  the  specimen 
increases  in  size  immediately  beyond  the  gage  length.  Any 
stretch  outside  the  gage  length  erroneously  credits  additional 
energy  to  the  specimen. 

Sound  specimens  of  good  malleable  iron  0.1  square  inch 
in  area  and  2  inches  long  showed  results  as  follows  when 
tested : 

Energy  •df  rupture  Elongation 

(foot  pounds  iper  (per    cent   an 

cubic   inidh)  2   imdh-es) 

755  15 


999  20 


The  relation  between  resistance  to  dynamic  tension  and 
elongation  is  plainly  'Shown  and  is  still  more  plainly  visible 

Fatigue,   Impact  Hardness  and   Wear 


by  examining  -the  following  tests  on  good  malleable  containing 
small   shrinks. 

Energy    of    iruiptuire 

(ifioiolt  (pounds  per 

icu'bic    indh) 





(per    'cent   in 

2   inic'hes) 

The  graph  in  Fig.  153  which  summarizes  these  data  indicates 
the  almost  direct  proportionality  of  elongation  and  resistance 
to  tensile  impact  even  when  the  former  is  artificially  affected 
by  mechanical  defects. 

































5               t 

3                                     10                                      15                                    20 

Per  Cent    Elonqation 

Fig.   153. — Effect  of  elongation  of   specimen  on  the  resistance  to  dynamic 

tensile  loads 

The  presence  of  temper  carbon  nodules  operates  just  like 
any  other  mechanical  discontinuity.  Accordingly  it  is  almost  im- 
possible to  obtain  consistent  results  in  tensile  impact  from  mal- 
leable. All  the  results  doubtless  are  lower  than  the  correct  value 
and  since  they  are  far  from  concordant  their  practical  interpre- 
tation is  doubtful.  At  best  the  test  is  poorly  suited  to  so  hetero- 
geneous a  material. 

From  'the  energy  of  rupture,  the  measured  elongation  and 
the  known  dimensions  of  the  specimen  we  can  calculate  a 
modulus  of  rupture  as  the  average  intensity  of  tensile  •  stress  in 
pounds  per  square  inch  developed  during  rupture  of  the  ma- 
terial. Disregarding  the  very  small  elastic  deformation  which 

320        American  Malleable  Cast  Iron 

has  disappeared  when  the  permanent  elongation  is  measured 
we  can  proceed  in  the  light  of  the  previous  formulas  to  solve 
the  equation: 

fs  =  KtEv 

for  K  t,  the  modulus  of  rupture.  The  values  of  js,  corre- 
sponding to  given  value  of  /,  are  shown  in  the  preceding  tables 
on  the  basis  of  v  being  unity. 

The  average  value  of  Kt  on  the  four  sound  specimens 
previously  quoted  was  58,600  pounds  per  square  inch,  the  three 
imperfect  ones  showing  in  order  3500,  4700,  and  5500  pounds 
per  square  inch. 

Unfortunately  the  static  tensile  properties  of  the  material 
were  not  actually  determined.  From  the  stress  strain  curve 
shown  in  Fig.  139  in  Chapter  XV,  we  may  derive  an 
approximation  of  the  value  of  K.  The  average  abscissa  (stress 
ordinate)  of  that  graph  is  about  0.88  times  the  stress 
art  rupture.  Using  K  as  0.14  we  can  calculate  t  in  the  ex- 

Kt  —  58,600  pounds  per  square  inch 

with  the  result  that  t  has  an  approximate  value  of  66,600 
pounds  per  square  inch. 

While  the  data  are  both  too  few  and  too  inaccurate  for 
definite  conclusion  there  is  a  presumption  at  least  that  in  ten- 
sion the  material  fails  under  impact  at  materially  higher  stresses 
than  under  static  loads  but  that  the  elongation  is  not  greatly 
different  in  the  two  conditions. 

The  effect  of  velocity  of  impact  on  maximum  stress  is 
among  the  most  interesting  but  least  understood  phenomena 
in  the  utilization  of  materials.  It  is  hoped  that  work  in  pre- 
paration under  the  author's  direction  will  be  productive  of 
more  accurate  and  useful  conclusions. 

A  number  of  tests  have  been  devised  in  which  repeated 
impact  is  applied.  Such  tests  must  be  closely  standardized 
as  to  the  form  of  specimen  and  the  energy  of  the  blow.  The 
amount  by  which  the  stresses  set  up  by  a  single  blow  exceed 
the  yield  point  greatly  affects  the  results  of  the  tests. 
Any  variable  in  design  or  material  which  affects  the  yield  point 

Fatigue,  Impact  Hardness  and   Wear 


of  the  specimen  as  a  whole  therefore  profoundly  alters  the  re- 
sult of  such  a  test. 

A  dynamic  test  developed  especially  for  application  to  mal- 
leable iron  was  devised  at  the  general  suggestion  of  the  late  B. 
J.  Walker  and  is  sometimes  known  by  his  name.  In  this  test 
a  wedge  specimen  6  inches  long  by  1  inch  wide,  tapering  from 
J/2  to  1-16  'inch  thick  is  used.  The  specimen  is  set  on  its 
thicker  end  on  the  anvil  of  a  drop  hammer  and  subjected  to 

Fig.   154. — Walker  test  wedges 

blows  of  70  foot  pounds.  The  first  blow  is  struck  straight 
down  on  the  point  of  the  wedge,  curling  it  over,  and  for  each 
succeeding  blow  the  specimen  must  be  held  so  that 
the  point  which  will  be  struck  by  the  hammer  is 
directly  over  the  point  of  support.  This  is  a  difficult 
requirement  to  fulfill  and  the  test,  while  measuring  a  very 
useful  property,  is  almost  incapable  of  quantitative  reproduc- 
tion and  is  accordingly  of  only  slight  interest  to  the  consumer. 

A  normal  malleable  is  supposed  to  survive  20  blows  (ag- 
gregating 1400  foot  pounds)  in  this  test  and  to  break  not 
more  than  1%  inches  from  the  thick  end  of  the  wedge.  A 
better  mechanical  execution  of  this  test  possibly  would  yield 


American  Malleable   Cast  Iron 

Fig.   155. — Behavior  of   malleable  iron  under   fatigue  as  a  rotating  beam 

results  of  value  and  has  been  studied  by  the  writer  for  some 

The  writer  has  been  informed  that  tests  by  the  Humphrey 
static  notched  bar  method  yield  valuable  data  as  to  brittleness 
but  has  not  personally  investigated  the  matter. 

Tests  can  readily  be  made  under  dynamic  stresses  of  the 
second  type,  involving  repeated  reversals  of  direction  under 
rather  small  loads.  Machines  of  the  Upton  Lewis  type, 
especially  when  equipped  for  alternate  torsion,  are  valuable  for 
this  purpose,  particularly  when  considerable  intensity  of  stress 
is  desired.  Machines  of  the  Wohler,  Whiter  Souther,  or  Far- 
mer-type apply  well  to  the  repetition  of  smaller  stresses  existing 
in  rotating  specimens  subjected  to  bending. 

W.  W.  Flagle  in  the  author's  laboratory  has  determined  the 
relation  between  maximum  fiber  stress  and  life  of  a  typical 
malleable,  using  the  Farmer-type  machine.  The  results  of  his 
investigation  are  shown  in  Fig.  155  in  which  life  is  plotted 
against  stress  to  a  logarithmic  scale  as  suggested  by  Moore.  It 
will  be  seen  that  the  fatigue  or  endurance  limit  of  malleable  is  at 
25,000  pounds  per  square  inch.  Malleable  will  resist  alterations 
of  stress  of  this  magnitude  indefinitely — certainly  hundreds  of 
millions  of  times.  Reference  should  be  made  to  Moore's  data 
for  similar  information  on  a  variety  of  rolled  products. 

Prof.  H.  F.  Moore  is  quoted  to  the  effect  that  ingot  iron 
(ferrite)  will  withstand  100,000,000  repetitions  of  a  stress  1.6 
times  its  proportional  limit,  as  determined  in  tension.  This 
would  indicate  the  probable  great  endurance  of  the  matrix 
of  malleable. 

Fatigue,  Impact  Hardness  and   Wear 


It  will  be  seen  that  much  remains  to  'be  done  in  the  quan- 
titative investigation  of  the  resistance  of  malleable  to  fatigue 
and  to  impact.  Fortunately,  qualitative  information  of  this 
character  is  readily  accessible  in  view  of  the  long  continued 
application  of  malleable  iron  in  the  industrial  arts.  The  prac- 
tical experience  which  attracted  consumers  to  this  product 
when  searching  for  a  'shock  resisting  material  and  in  a  period 
when  methods  of  tests  and  metallography  were  practically  un- 
known seems  to  have  been  well  founded. 

A  logical  reason  now  is  available  for  this  quality.  Being 
largely  ferrite,  malleable  is  soft  and  ductile,  as  are  all  other 
materials  in  which  ferrite  predominates.  Wrought  iron  is  a 
conspicuous  example  of  such  materials;  malleable  is  not  as 
ductile  as  wrought  iron  because  of  the  temper  carbon  present. 
Its  resistance  to  deformation  and  shock,  however,  depend  upon 
this  principle. 

Malleable  lias  a  further  great  advantage  over  many  other 
materials  in  that  the  temper  carbon  granules,  while  of  a  form 
to  affect  the  physical  properties  only  to  a  relatively  slight  ex- 

Fig.    156. — Separation   of   grains   by   repeated   cross   bendings 

324  American   Malleable   Cast  Iron 

tent,  operate  as  a  hindrance  to  failure  under  alternating  stresses 
by  fatigue.  Such  failures  frequently  occur  by  the  penetration 
of  a  crack  'between  adjacent  grains  of  the  metal.  When  such 
a  crack  begins  to  form  in  malleable  it  does  not  penetrate 
far  before  it  strikes  one  or  more  carbon  granules.  These 
stop  its  further  progress  just  as  a  hole  drilled  at  the  end  of 
a  crack  in  a  bell  prevents  the  growth  of  the  crack. 

The  best  evidence  available  as  to  the  shock  resisting  quali- 
ties of  the  material  are  derived  from  the  years  of  service  which 
properly  made  malleable,  has  given  in  draft  gears,  rail  anchors, 
automobile  hubs  and  spring  brackets,  car  couplers  (until  high 
train  loads  forced  the  'adoption  of  a  material  capable  of  higher 
unit  stresses),  and  an  indefiniite  number  of  similar  applications. 

For  some  kinds  of  service  the  fitness  of  a  material  for  the 
use  intended  may  depend  not  so  much  upon  its  strength  under 
load  as  upon  its  machineability,  resistance  to  abrasion,  co- 
efficient of  friction  and  similar  properties. 

The  property  which  enables  a  material  to  resist  cutting  or 
wear  is  somewhat  loosely  called  hardness.  Unfortunately 
this  term  is  not  clearly  defined  and  often  it  is  misinterpreted. 
Moreover,  the  commercial  methods  for  measuring  hardness  in 
metals  actually  measure  resistance  to  penetration  under  defined 
conditions' — a  property  bearing  no  practical  or  theoretical  rela- 
tion to  hardness  as  understood  in  'the  definition  given  above. 

Two  methods  of  measuring  so  called  hardness  a'fe  in  com- 
mon use-  In  Brinell's  method,  hardness  is  determined  by  the 
depth  to  which  a  10-millimeter  ball  will  penetrate  under  a 
load  of  3000  kilograms.  In  Shore's  method,  the  rebound  of  a 
hammer  falling  from  a  fixed  height  measures,  in  effect,  the 
work  absorbed  by  the  plastic  deformation  of  the  material  un- 
der a  standard  load.  The  results  of  the  Brinell  test  bear 
a  fairly  close  relationship  to  the  ultimate  strength  of  the 
material,  while  the  data  obtained  by  the  Shore  method  should 
conform  to  the  elastic  limit. 

The  Brinell  number  of  normal  malleable  cast  iron  is  from 
about  101  to  145  and  increases  as  does  the  tensile  strength 
with  decreasing  carbon.  Common  values  are  around  110-120. 
Fig.  157  shows  the  relation  between  the  Brinell  number  and 

Fatigue,   Impact  Hardness  and   Wear 


the  strength  of  a  wide  range  of  malleable  iron.  The  heavy 
line  indicates  the  probable  relationship  and  the  shaded  area  the 
limits  of  variation  from  the  probable  value.  The  scleroscope 
number  is  somewhat  erratic,  running  from  about  15  to  about  20. 
The  Shore  nurriber  actually  is  surprisingly  constant  in 
malleable  of  quite  variable  tensile  properties.  Some  experi- 
mental data  as  to  the  relation  between  this  hardness  number 





v7*    W 

YA    M 


Waximum_    7//A 








36  38  4O  42  44-  46  46   5O  52  54  S£  53    £O 

Fig.  157. — Relation  between  Brinell  number  and  strength  of  malleable  iron 


and  the  Brinell  number  are  presented  in  Fig.  158.  The  explana- 
tion of  the  approximate  constancy  of  the  Shore  number  is  as 
follows : 

The  variation  in  physical  properties  of  malleable  are  due 
primarily  to  the  ratio  of  ferrite  to  temper  carbon  and  not  to 
variations  'in  -the  properties  of  the  ferrite.  The  Shore  test 
being  made  on  an  almost  microscopic  area  determines  only  the 
properties  of  the  ferrite.  If  by  accident  a  temper  carbon 
grain  is  struck  no  rebound  at  all  is  observed-  The  composition 
of  the  ferrite  is  not  sufficiently  variable  to  alter  its  physical 


American  Malleable   Cast  Iron 

Neither  of  -the  hardness  numbers  bears  any  particular  re- 
lation to  completeness  of  anneal.  White  iron  is  harder  than 
malleable  so  that  the  effect  of  annealing  is  to  soften  the  metal 
under  both  tests.  Under  commercial  conditions,  however,  an- 
nealing is  almost  never  so  far  from  complete  that  this  fact 
is  of  any  value  in  inspecting  material.  Malleable  castings  which 
are  sufficiently  annealed  to  pass  any  ordinary  inspection  usually 






tf/'/sy^'//  M&s-t/sy&^s 

Fig.    \*&. — Graph    showing    comparison    of    Brinell    and    Shore    numbers 
indicating  relation  between  them  is  not  definite 

contain  only  very  small  amounts  of  ungraphitized  carbides.  The 
remaining  combined  carbon  is  either  found  as  cementite  in  very 
minute  grains  scattered  throughout  the  castings  or  as  a  thin 
layer  of  pearlite  just  under  the  surface. 

The  former  condition  would  have  no  effect  on  the  Brinell 
hardness  and  would  affect  the  scleroscope  hardness  only  if 
the  hammer  struck  such  a  grain  by  accident.  The  thin  sheet 
of  pearlite  does  not  increase  the  <,Brinell  hardness  appreciably, 
since  the  pearlite  layer  is  merely  crushed  down  upon  the  deeper 
material  which  is  soft.  The  Shore  number  may  be  affected  by 

Fatigue,   Impact  Hardness  and  Wear 327 

pearl ite  if  this  'be  present  at  the  finished  surface  of  this 
sample  and  if  the  layers  are  heavy  enough  to  absorb  the  im- 
pact. Neither  of  these  conditions  usually  exists  for  the  pear- 
lite  is  originally  covered  with  ferrite  and  if  in  producing  a 
finished  flat  surface  for  test  any  considerable  amount  of  ma- 
terial is  removed  the  pearlite  layer  may  be  completely  de- 
stroyed. The  point  'has  been  emphasized  by  Prof.  Touceda 
and  also  by  W.  R.  Bean. 

Therefore  these  tests  are  not  directly  applicable  to  the 
commercial  valuation  of  malleable  with  reference  to  its  cutting 
properties.  The  important  considerations  in  industrial  uses  of 
malleable  involve  cutting  hardness  which  is  undesirable  in 
fabricating  the  product  in  the  machine  shop,  and  wearing  hard- 
ness or  resistance  to  abrasion,  which  resists  the  destruction  of 
a  bearing  or  similar  detail  where  subjected  to  friction. 

These  two  conditions  are  different  manifestations  of  near- 
ly the  same  property.  Ease  of  machining  and  resistance  to 
wear  are  incompatible  with  one  another.  No  direct  means  of 
measuring  cutting  hardness  are  known.  The  hardness  of  min- 
erals is  measured  by  comparison  with  an  arbitrary  scale  rang- 
ing from  talc,  having  a  'hardness  designated  as  V  to  diamond, 
with  a  hardness  of  10.  Any  given  mineral  can  be  rated  by 
determining  between  which  two  numerals  its  hardness  lies. 
Thus,  pyrite,  which  scratches  feldspar,  hardness  6,  but  is 
scratched  by  quartz,  hardness  7,  is  given  an  intermediate  num- 
ber, in  this  case  6.3.  On  this  'scale  iron  has  a  hardness 
of  about  4  or  5  and  steel  a  hardness  of  from  5  to  8.5.  This 
test  besides  being  very  unsensitive  can  be  applied  only  to  the 
extreme  surface  of  a  metal.  In  the  case  of  malleable  this 
always  is  ferrite,  which  shows  a  hardness  of  4. 

Turner  has  devised  a  method  based  on  cutting  a  line 
into  the  surface  of  the  material.  This  is  done  by  pressing  the 
V-shaped  nose  of  a  diamond  against  the  metal  under  a  def- 
inite pressure.  The  cross  section  of  the  furrow  cut,  as  meas- 
ured by  the  width  of  the  groove,  is  intended  to  be  the  measure 
of  cutting  hardness.  This  method  is  applicable  only  to  the  sur- 
face of  an  article.  Since  the  surface  must  be  smooth,  it  is  diffi- 
cult to  apply  this  test  to  malleable  containing  a  pearlite  layer,  as 

328 American   Malleable   Cast  Iron 

pointed  out  in  the  discussion  of  the  Shore  hardness.  The 
test  is  not  used  extensively,  and  the  writer  knows  of  no  data 
obtained  from  its  application  to  malleable  iron- 

Similar  tests,  made  by  scratching  polished  samples  and 
examining  the  scratch  under  the  microscope  indicate  that  the 
hardness  of  the  micro-constituent  present  in  normal  hard  iron 
and  malleable  iron  is  in  the  following  order:  Ferrite,  pearlite, 
cementite.  Ferrite  is  soft  and  cementite  nearly  as  hard  as 
carborundum,  as  measured  by  resistance  to  scratching. 

Study  of  Cutting  of  Metals 

The  principles  underlying  the  machining  of  metals  have 
been  investigated  by  a  number  of  experimenters,  notably,  Nich- 
olson, Frederick  Taylor  and  Herbert.  The  special  case  of 
machining  by  twist  drills  has  been  still  more  fully  investi- 
gated— for  example,  in  the  engineering  experiment  station  of 
the  University  of  Illinios. 

While  these  studies  have  thrown  much  light  upon  the  prin- 
ciples underlying  the  cutting  of  metals  and  liave  served  in 
some  cases,  notably  in  Herbert's  experiments,  to  test  the  qual- 
ity of  cutting  tools,  they  were  not  generally  conducted  so  as 
to  develop  any  technique  for  the  testing  of  a  material  for 
machineability.  Accordingly,  no  method  is  yet  available  for 
determining  how  readily  an  existing  structural  detail  can  be 
machined.  Therefore  it  is  not  surprising  that  there  are  no 
means  for  quantitatively  comparing  the  machining  properties 
of  malleable  cast  iron  with  those  of  similar  materials. 

However  the  fundamental  relationships  involved  are  eas- 
ily summarized.  To  the  consumer,  machineability  means  the 
removal  of  the  required  amount  of  metal  in  the  minimum 
of  time  and  with  the  minlimium  of  tool  destruction.  Many 
investigations  have  approached  the  subject  by  measuring  the 
load  on  the  nose  of  the  lathe  tool.  Nicholson  measured  this 
load  parallel  to  three  rectangular  co-ordinates — radial,  tangential, 
and  axial — with  reference  to  the  revolving  specimen  and  used 
only  two  materials,  soft  and  medium  steel.  His  work  resulted 
in  a  mass  of  data  concerning  the  relation  between  the  cutting 
angles  of  the  tool  and  the  direction  and  magnitude  of  the 

Fatigue,   Impact  Hardness  and   Wear 329 

resultant  forces.  He  also  made  a  limited  number  of  tests 
on  *he  effect  of  cutting  angles  on  tool  life. 

For  'the  present  purpose  his  work  may  be  summarized  as 
having  demonstrated  that  the  tangential  thrust  on  the  tool 
is  independent  of  the  cutting  speed  and  that  the  life  of  the 
tool  increases  as  the  cutting  angle  increases.  Taylor  in  his 
monumental  monograph  "The  Art  of  Cutting  Metals,"  covered 
exhaustive  investigations  on  feeds,  depth  of  cut,  form  of  tool, 
cutting  speed  load  on  the  tool  point  and  tool  life.  He  deduced 
the  fact  that  the  load  on  the  tool  point  is  dependent  only 
on  the  area  of  the  chip  being  removed  and  the  material 
being  cut  and  independent  of  the  cutting  speed,  form  of  tool, 
relation  between  depth  of  cut  and  feed,  or  any  other  varia- 

This  seems  to  indicate  that  the  load  on  the  tool  point 
per  unit  area  of  cut  is  a  constant,  readily  determined  for  a 
given  material.  This  is  true,  'but  unfortunately  the  deter- 
mination of  this  constant  has  no  practical  use  since  Taylor 
also  proved  conclusively  that  no  determinable  relationship  ex- 
ists between  this  constant  and  tool  wear  or  economical  cut- 
ting speed. 

Herbert  has  shown  from  Taylor's  data  that  tool  failure  re- 
sults from  the  heat  evolved  in  cutting  and  has  deduced  a  for- 
mula for  determining  the  relation  between  the  tool  temperature 
and  feed,  cut,  and  speed.  He  also  has  proved  that  the  most 
economical  tool  service  corresponds  to  a  definite  tempera- 
ture which  is  a  function  of  the  tool  steel  used. 

From  this  it  will  foe  seen  that  all  of  the  work  pre- 
viously done  has  not  resulted  in  conclusions  applicable  to  the 
defining  of  the  machineability  of  a  given  material  in  terms 
of  permissible  cutting  speeds. 

Consumer  Wants  Cutting  Speed 

In  general  the  consumer  is  not  interested  in  the  load  at 
the  tool  point,  since  he  is  quite  willing  to  adopt  machine  and 
tool  designs  capable  of  sustaining  any  loads  which  may  be 
developed,  providing  only  -he  is  informed  as  to  the  probable 
stress  to  be  encountered.  The  power  consumed  in  removing 


American  Malleable   Cast  Iron 

the  material  also  is  of  little  interest,  since  this  is  not  a  major 
item  of  expense  and  can  be  met  by  the  installation  of  a  suffi- 
ciently heavy  drive.  His  chief  requirement  is  a  fast  cutting 
speed  with  long  tool  life.  Tool  life  when  determined  by  nor- 


<0'  1600 

^  1400 

'5  1300 





<O        -)-x 

Q£         £3 

1  * 

\  z< 

\     .19 


fensi/e  Strength  in  Pounds  Per  Square  Inch. 
45000                                 50000 



__  — 






.>  - 








—  Corrects. 

'0^     /^OA- 


Relation  Between  L  oad  on  One  Inch 
D/e  and  rensi/e  Properties. 



















fte/atf  on  Between  Dri/  /ing  Quo/ityond  \ 
Tensr/e  <Strengff)of^/7o//eQb/e.             \ 



jqooo                        45yooo                            50.000 
Pounds  Per  SQuare  Inch 

Fig.   159. — Tests  of  machining  properties  of   malleable  cast  iron 

The  curves  are  plotted  from  data  presented  by  Edwin  K.  Smith  and 
William  Barr,  Milwaukee,  in  a  paper  prepared  for  the  American  Found- 
rymen's  association,  1919. 

mal  conditions  is  fixed  by  the  working  temperature  of  the  tool, 
determined  by  cutting  conditions  and  the  material  being  ma- 
chined. Suitable  investigation  by  Herbert's  methods  should 
yield  useful  results  in  the  relative  rating  of  different  metals, 
but  the  data  are  not  available. 

Smith  and  Barr  have  attempted  to  determine  the  relative 

Fatigue,  Impact  Hardness  and   Wear  331 

machineability  of  different  samples  of  malleable  and  to  com- 
pare the  data  with  that  for  other  materials.  Their  experiments 
were  based  on  the  torque  required  to  cut  threads  into  the  dif- 
ferent samples  with  two  dies  taken  as  standards  and  also  by 
measuring  the  penetration  per  revolution  of  a  standard  drill 
under  a  standard  load. 

Unfortunately  the  data  are  incapable  of  conversion  into 
absolute  figures.  Smith  and  Barr  apparently  felt  that  they  had 
secured  evidence  pointing  toward  the  fact  that  iron  high  in 
tensile  strength  is  relatively  difficult  to  machine.  The  author 
does  not  feel  that  this  conclusion  is  necessarily  justified  by  the 
observed  facts.  Fig.  159  shows  graphically  the  results  of  their  in- 
vestigations and  in  the  writer's  opinion  they  indicate  that  the 
machineability  of  normal  malleable  is  within  the  limit  of  error 
of  the  data. 

However  these  investigators  have  accumulated  useful  data 
comparing  the  resistance  to  drilling  of  malleable  cast  iron,  gray 
cast  iron  and  steel-  Their  results  indicate  that  the  penetration 
of  a  drill  under  standard  conditions  is  at  the  rate  of  0.249 
inch  per  minute  and  0.196  inch  per  minute  in  two  specimens 
of  gray  iron;  0.209  to  0.240  inch  per  minute  in  17  samples 
of  malleable  and  0.052  to  0.085  inch  per  minute  in  three 
samples  of  steel.  This  proves  the  general  thesis  that  malleable 
is  comparatively  easy  to  machine. 

An  exhaustive  study  of  all  types  of  machining  operations, 
using  the  best  equipment  known,  is  in  progress  under  the 
writer's  direction.  In  connection  with  this  work,  W.  W.  Flagle 
has  gathered  data  as  to  the  load  on  twist  drills  of  standard  form- 
when  drilling  fully  annealed  malleable. 

The  investigation  included  a  study  of  the  effect  of  drill 
diameter,  feed,  -speed  and  character  of  metal  being  cut.  The 
effect  of  drill  form,  of  lubricants  and  the  life  of  drills  is 
being  further  investigated. 

The  work  is  far  too  voluminous  for  presentation  in  detail 
in  the  present  connection  and  is  reserved  for  publication,  in 
a  more  appropriate  place.  A  few  of  tbe  more  interesting 
conclusions  may  be  abstracted  as  follows. 


American   Malleable   Cast  Iron 

The  torque  on  a  drill,  cutting  malleable  iron  varies  as 
the  square  of  the  diameter  and  approximately  directly  as  the 
feed.  The  thrust  varies  directly  as  the  feed  and  approximate- 
ly as  'the  drill  diameter.  The  effect  of  speed  on  torque  and 
thrust  is  but  small  for  rates  from  40  to  640  revolutions 




































































-—  —  . 

—  - 


























"~  — 





h^'Fer  /?&v. 



itH  —  1 

?  200  300  400  $0  600    $25.005  Dl         .02                    .04 
Sfiee&/s?  /&?M.               Feed  Per  tfe\/o/vf/  on 

J/?d-  feeds 

Fig.    160.  —  Graph    showing    values    of  a    in   drilling    formula 

per    minute.       Both    loads    decrease  slightly     with    increasing 

speed   and  are   more   nearly  constant  with   variations   in   speed 
at  high  speeds  than  at  low. 

Representing    by    Tv    the    torque    and    by    Tt    the    thrust 

of  a  drill  of   diameter  df  running  at  s  revolutions  per  minute 

with  a  feed,  /,  in  a  certain  uniform  iron 


Tt  =  bfd 

Fatigue,   Impact  Hardness  and   Wear 


in  which  a  and  b  are  constants  depending  on  sf  t,  and  d. 
The  values  of  a  and  b  can  'be  interpolated  from  the  graphs 
in  Fig.  160  and  161  respectively. 

The   drilling  properties  are    further   affected   by   variations 
in    the    character   of    the    metal-      The    investigation    disclosed 














I  I  I 





400  3W   600 



J"    M 

Fig.   161. — Graph  showing  values  of  b  in  drilling  formula 

that  machining  stresses  were  not  related  to  either  Brinell  num- 
ber or  strength  as  effect  to  cause.  However,  there  is  a  gen- 
eral coincidence  between  the  three  properties  in  completely 
annealed  malleable. 

The  data  of  Figs.  160  and  161  were  obtained  from  malle- 
able equivalent  to  a  tensile  strength  of  52,000  pounds  per  square 
inch  and  a  Brinell  number  of  120.  In  Figs.  162  and  163  the 
effect  of  Brinell  number  and  strength  on  Tv  and  Tt  are  plotted 
in  the  form  of  coefficients  for  reducing,  the  previously  calcu- 
lated values  to  suit  other  tensile  or  hardness  properties. 


American   Malleable   Cast  Iron 

The  observations  in  a  measure  substantiate  Smith  and 
Barr's  ideas  as  to  the  increased  machining  difficulty  of  stronger 
metal.  Apparently  there  is  a  variation  of  from  25  to  30  pet- 
cent  in  the  stresses  developed  as  between  the  weakest  and 
strongest  malleable. 

These  variations  are  not  nearly  sufficient  to  bridge  the 
gap  between  malleable  and  even  the  softest  steel. 




Fig.    162. — Correction    factor    for    drill    torque    and    thrust    in    terms    of 

ultimate    strength 

It  is  again  to  be  emphasized  that  neither  the  author's  data 
nor  that  of  Smith  and  Barr  can  be  interpreted  in  terms  of 
tool  life.  Furthermore,  it  must  be  clearly  remembered  that  the 
data  were  all  obtained  on  completely  graphitized  material  and 
that  nothing  heretofore  sajid  has  any  relation  whatever  to  white 
edged  or  white  material  resulting  from  mischances  in  annealing. 
The  subject  has  already  been  referred  to  in  connection  with 

Fatigue,  Impact  Hardness  and   Wear 


the  discussion  of  Brinell  numbers  where  it  was  shown  that 
such  mischances  do  not  necessarily  influence  the  hardness  test. 
They  do,  however,  greatly  affect  machineability  both  with  re- 
spect to  tool  life  and  stresses. 

The   machining   difficulties   occasionally   encountered   might 
be   explained   on   either   of   three   grounds.    First,   the   material 




Fig.    163. — Correction   factor   for   drill   torque   and   thrust   in  terms   of 

Brinell  number 

may  be  so  tough  'that  the  heat  developed  per  unit  of  time  causes 
the  tool  temperature  to  increase  rapidly.  The  tool  fails  for  per- 
fectly normal  causes  but  under  much  accelerated  conditions. 
Second,  the  material  may  contain  particles  sufficiently  hard  to 
work  as  an  abrasive  and  so  destroy  the  cutting  edge.  Third, 

336 American   Malleable   Cast  Iron 

the  material  may  set  up  so  heavy  a  tangential  load  in  the 
tool  point  as  to  cause  it  to  break  off  irrespective  of  the  failure 
of  the  cutting  edge. 

A  study  of  abnormally  early  tool  failures  seems  to  indi- 
cate the  occurrence  of  failures  of  all  three  types-  Since  all 
malleable  cast  iron  consists  only  of  ferrite  and  temper  carbon 
it  is  difficult  to  see  how  any  great  difference  could  exist  between 
different  products  varying  only  in  the  percentage  of  temper 
carbon  present.  This  is  all  the  more  true  since  in  general  the 
cutting  is  in  a  region  where  relatively  little  carbon  remains  due 
to  decarburization  in  anneal- 

In  the  case  of  imperfectly  'annealed  iron  a  condition  ac- 
counting fof  any  or  all  these  causes  of  failure  may  exist. 
White  cast  iron  is  known  to  exert  very  heavy  unit  stress  on  the 
tool  point,  hence  a  metal  so  imperfectly  annealed  as  to  retain 
much  of  its  original  pearlite-cementite  dendritic  structure  would 
set  up  abnormal  tool  loads  and  cause  a  failure  of  the  third 

Material  in  which  cooling  'has  been  so  slow  that  all  pearlite 
is  graphitized  but  in  which  some  cementite  persists  would  pro- 
duce failures  of  the  second  class.  Cementite  is  an  exceedingly 
hard  ingredient,  the  hardest  of  any  carbon-iron  alloy.  Its  hard- 
ness on  the  mineralogical  scale  is  between  8  and  9,  since  it 
is  harder  than  the  hardest  steels.  In  imperfect  malleable  of 
this  kind  it  would  be  found  scattered  as  granules  through  the 
ferrite.  Being  present  In  very  small  amount  only,  it  could 
hardly  exert  any  very  great  effect  on  the  ferrite  mass  in 
which  it  is  imbedded  and  therefore  is  not  likely  to  either  in- 
crease the  tool  temperature  or  the  load  thereon.  The  tool  edge 
however,  will  encounter  those  granules  lying  in  the  finished 
surface  and  these  grains  will  rapidly  wear  away  the  cutting 
edge  which  rubs  against  them. 

Failures  of  the  first  class  are  very  largely  due  to  so 
called  "picture  frame"  iron  in  which  there  remains  a  consider- 
able pearlite  layer  just  under  the  surface.  This  layer  is  identical 
in  composition  and  properties  with  annealed  tool  steel.  As 
such  the  cutting  speed  will  not  be  great  before  sufficient  heat 
is  generated  to  rapidly  destroy  the  tool.  Unusually  bad  cases 

Fatigue,  Impact  Hardness  and  Wear 337 

of  this  character  may  also  produce  failures  of  the  third  class. 
It  should  'be  remembered  that  all  normally  made  malleable 
is  easily  machined,  there  being  minor  differences  only  between 
the  machineability  of  malleable  of  varying  composition.  When 
machining  difficulties  are  encountered  the  explanation  general- 
ly is  due  to  failures  of  execution  in  individual  cases  rather 
than  to  the  character  of  the  product  as  a  whole. 

Resistance  to  Friction 

To  all  intents  and  purposes,  resistance  to  frictional  wear 
obviously  is  the  converse  of  machineability.  Experience  seems 
to  indicate  that  the  most  successful  bearing  metals  are  those 
consisting  of  fairly  soft  matrix  in  which  a  relative  hard  con- 
stituent is  imbedded.  The  hard  constituent  takes  the  wear  and 
is  supported  by  the  soft.  Further,  the  soft  constituent  wearing 
down  a  little,  furnishes  the  certainty  of  a  supply  of  lubricant  to 
the  bearing.  The  soft  ingredient  is  further  desirable  since  if  a 
grain  of  abrasive  enters  the  bearing  and  lodges  tightly  in 
the  bearing  metal  it  will  >soon  cut  away  the  rotating  mem- 
ber where  the  latter  rubs  against  it.  With  a  soft  bearing  metal 
the  grit  will  at  most  cut  a  groove  in  the  easily  replaced  bearing 
without  damage  to  the  shaft. 

Since  malleable  does  not  contain  the  hard  skeleton  or 
grain  required  to  promote  long  life  it  cannot  be  regarded  as 
suitable  metal  to  resist  wear.  By  'analogy  also  with  gray  iron 
this  conclusion  seems  warranted.  Extremely  soft  gray  irons, 
which  resemble  malleable  more  closely  than  those  containing 
more  combined  carbon,  are  inferior  to  the  harder  irons  as 
bearing  materials. 

Malleable  is  not  a  suitable  material  of  construction,  where 
the  major  requirement  is  resistance  to  wear,  as  for  instance 
in  journal  bearing's. 

It  will  of  course  resist  minor  friction  incident  to  other 
service.  .  Under  such  circumstances,  the  conditions  as  to  hard- 
ness and  smoothness  of  the  material  rubbing  against  it  is  of 
prime  importance  in  determining  the  service  to  be  expected. 
Determinations  of  the  coefficient  of  friction  for  the  metal  are 
not  available.  While  they  would  be  highly  interesting,  they 

338  American   Malleable   Cast   Iron 

are  not  of  great  practical  application  because  of  the  general 
unsuitability  of  malleable  for  friction  service  and  because  under 
normal  lubricating  conditions  in  machine  parts  there  is  not 
metallic  contact  between  shaft  and  bearing.  Therefore  the 
friction  losses  depend  mainly  upon  the  lubricant  and  not 
upon  the  material  of  the  shaft  and  its  support. 



IN  CONSIDERING  the  behavior  of  malleable  cast  iron  under 
mechanical  stress  we  have  noted  that  like  most  other  materials 
its    deformation,    or   strain,    under    load    is    of    two    entirely 
distinct  characters,  depending  upon  the  intensity  of  the  stress. 
Under  light  loads  the  deformation  is  elastic;  that  is,  it  is  pro- 
portional to  the  applied  stress  and  is  not  permanent,  the  metal 
returning  to  its  original  dimensions  upon  the  removal  of  the  load. 
At  higher  stresses  the  strain  increases  very  rapidly  and  the  spe- 
cimen becomes  permanently  deformed. 

This  change  of  form  is  termed  "plastic"  deformation  as  dis- 
tinguished from  "elastic,"  and  especially  characterizes  ductile 
metals.  Much  interesting  work  has  been  done  in  the  investiga- 
tion of  the  phenomenon  of  plastic  flow,  the  property  by  virtue  of 
which  a  material  is  malleable  and  ductile.  The  property  is 
usually  measured  in  terms  of  yield  point,  reduction  in  area  and 

Nutting  has  developed  the  thesis  that  plastic  strain  may  be 
expressed  as  the  product  of  constant  and  exponential  functions 
of  the  stress  and  time.  In  other  words,  the  strain  is  measured 
by  the  expression  ASxty  where  S  is  stress,  t  time  and  A,  x  and  -v 
characteristics  of  the  material.  Hook's  law  is  a  special  case  of 
this  formula  when  x=\  and  y==0. 

The  author  has  no  desire,  in  the  present  connection,  to  at- 
tempt any  exposition  of  the  theoretical  aspects  of  plastic  flow. 
However,  since  malleable  cast  iron  is  in  quite  a  marked  degree 
capable  of  plastic  deformation,  and  in  fact,  owes  many  of  its 
most  valuable  properties  to  this  property,  it  seems  well  to  sum- 
marize the  effect  of  plastic  deformation  on  the  metal. 

Summary   of   Theory 

As  has  been  shown,  malleable  is  in  effect  a  mass  of  ferrite 
made  up  of  individual  grains.  Each  grain  is  made  up  of  many 
crystals  all  oriented  in  space  in  the  same  direction.  The  several 

340  American  Malleable    Cast  Iron 

grains  are  held  together,  according  to  the  now  generally  accept- 
ed view,  by  a  thin  layer  of  amorphous  (non-crystalline)  iron 
acting  as  a  cement.  This  amorphous  iron  is  supposed  to  be 
stronger  than  the  crystalline  variety  and  is  supposed  to  behave 
like  a  very  viscous  liquid.  It  is  also  supposed  that  crystalline 
iron  will  go  over  into  amorphous  iron  under  heavy  stresses. 

The  behavior  of  a  metal  under  even  the  simplest  stresses 
is  as  a  rule  complex.  Even  when  a  stress  is  applied  in  only 
one  direction  the  behavior  of  the  material  indicates  that  com- 
plex systems  of  forces  result.  While  we  speak  of  the  elonga- 
tion or  compression  of  a  metal  these  terms  are  in  a  sense  mis- 
nomers, since  solids  are  but  slightly  compressible  in  the  sense 
of  a  decrease  in  volume  or  mutatis  mutandis  capable  of  elonga- 
tion. Metals  compressed  or  lengthened  by  plastic  deforma- 
tion do  not  materially  gain  or  lose  bulk.  For  example  a  speci- 
men compressed  until  it  was  only  one-fourth  its  original  height 
had  its  density  reduced  from  7.206  to  7.196  in  the  process,  a 
change  in  the  opposite  direction  to  what  might  be  expected. 

Behavior  of  Specimens 

The  increase  or  decrease  of  dimensions  parallel  to  the  di- 
rection of  applied  stress  is  made  up  by  decreases  or  increases  of 
cross  section  in  a  plane  normal  to  the  axis  of  stress;  the  tensile 
specimen  necks  in,  the  compression  specimen  becomes  barrel 

We  note  also  that  plastic  materials  do  not  fail  in  tension  or 
compression  in  a  plane  normal  to  the  stress.  The  tension  speci- 
men shows  a  cup  shaped  fracture,  at  least  on  one  side  of  the 
break.  The  compression  specimen  tears  apart  either  in  a  plane 
approximately  at  45  degrees  to  the  direction  of  stress,  or  more 
rarely  on  a  conical  surface  whose  axis  of  symetry  coincides  with 
the  direction  of  load. 

From  these  observations  it  is  evident  that  there  is  a  consid- 
erable motion  of  translation  within  the  stressed  material  in  di- 
rections at  right  angles  to  the  direction  of  the  applied  stress. 
This  rearrangement  may  conceivably  be  of  two  kinds  in  a  ma- 
terial composed  of  crystalline  grains  either  a  deformation  of 
the  individual  grain  (intragranular)  or  a  separation  and 

Plastic  Deformation  341 

rearrangement  of  the  grains  at  their  boundaries  (intergranular). 

Both  phenomena  are  easily  recognized.     A  deformation  of 

the  grain  itself  is  accomplished  by  a  shearing  of  the  grain  along 

Fig.   164. — Slip  bands  in  ferrite  of  malleable  iron 

Nitric  acid  etch  1000  diameters 

Note  that  there  is  but  little  evidence  of  any  separation  at  grain  boundaries 

mtragranular  crystal  boundaries.  Such  a  slip,  if  occurring  in 
a  grain  in  a  polished  surface,  shows  a  series  of  parallel  lines 
on  the  polished  surfate  which  are  fine  grooves  and  ridges  in 
the  originally  plane  surface. 

Fig.  164  shows  a  micrograph  at  1000  diameters  of  such  slip 
bands  in  a  ferrite  grain  in  malleable  cast  iron.     Such  a  deforma- 


American  Malleable   Cast  Iron 

tion,  increased  in  magnitude,  may  result  in  the  rupture  of  the 
grain  itself  at  right  angles  to  the  slip  bands,  as  shown  in  Fig.  165, 
or  by  producing  such  a  distortion  of  the  grains  that  it  can  no 
longer  articulate  with  the  surrounding  grains  closely  enough  to 
be  held  to  them  by  the  cement  of  amorphous  iron  at  the  bound- 

Change  of  Structure  When  Deformed 

On  the  other  hand  examination  of  the  originally  polished 
plane  surface  of  a  specimen  parallel  to  the  direction  of  stress 
which  had  failed  by  primary  intergranular  fracture  would  show 

Fig.   165. — Intragranular   fracture  of  a   ferrite  grain   in  malleable 

Nitric  acid  etch  1000  diameters 

Note  that  the  path  of  rupture  has  advanced  about  two-thirds  through  the 

grain  at  right  angles   to  the   slip  bands 

no  slip  bands  but  a  considerable  displacement  of  the  polished 
surfaces  of  the  individual  grains  from  their  initial  location  in 
the  polished  plane  provided  the  failure  was  due  to  shear  at 
the  grain  boundaries.  On  the  other  hand,  if  failure  was  due 
to  forces  having  a  tensile  component  normal  to  the  grain 
boundary,  the  separation  of  originally  adjacent  grains  would 
be  shown. 

Where  the  conditions  have  been  such  as  to  produce  fairly 
great  plastic  deformation  it  may  even  be  possible  to  note  the 
effect  of  intragranular  flow  in  the  changed  orientation  of  the 
polygons  marking  the  individual  grains. 

Plastic  Deformation 


In  unworked  ductile  metal  there  is  no  preference  as  to  the 
direction  of  the  longer  diameters  of  the  grains  in  any  given 
surface  nor  are  the  diameters  in  various  directions  widely 
different.  After  plastic  deformation  however  the  originally 
equi-axed  grains  may  be  flattened  into  sheets,  drawn  out  into 
threads,  etc.,  etc.,  depending  upon  the  character  of  the  stress 
and  the  direction  of  the  stress  with  reference  to  the  polished 

Fig.   166. — Intergranular   failure  of  malleable 

Nitric  acid  etch  400  diameters 

Note  that  the  surfaces  of  the  different  grains  no  longer  seem  to  be  in  the  same  plane 

surface  under  examination.  Of  course  it  is  obviously  necessary 
that  such  changes  of  form  can  be  detected  best  in  a  plane 
parallel  to  the  direction  of  load  and  are  visible  only  as  changes 
of  grain  size  in  a  plane  normal  to  the  deforming  stress. 

Microscopic  examination  of  the  path  of  rupture  through  a 
metal,  of  the  deformation  of  grains  under  load  or,  when  applied 
to  surfaces  prepared  before  the  application  of  the  stresses,  of 
intragranular  slip  and  intergranular  displacements  is  capable  of 

344  American   Malleable   Cast   Iron 

interesting  disclosures  as  to  the  mechanism  of  plastic  deforma- 
tion or  ultimate  failure  under  various  types  of  stress. 

Shows  Two  Systems  of  Slip  Bands 

A  very  cursory  summary  of  the  changes  in  malleable  is  at- 
tempted in  the  accompanying  photomicrographs.  .Fig.  166  shows 
an  unusual  failure  of  intergranular  type.  It  will  be  seen  that 
at  several  points  the  grains  have  the  appearance  of  being  above 
or  below  the  general  surface.  These  grains  have  slipped  not 

Fig.  167. — Ferrite  grains  in  malleable,  showing  slip  in  two  planes  at  right 


Nitric  acid  etch  400  diameters 

Note   the  cohesion   at  grain   boundaries   even   after   severe  plastic   deformation 

on  the  crystal  faces  within  the  grains  but  at  the  surface  of 
contact  of  adjacent  grains.  The  field  of  view  is  near  the  com- 
pression side  of  a  piece  distorted  by  cross  bending  and  it  is  pos- 
sible that  this  slip  at  grain  boundaries  produces  the  white  so 
called  compression  fracture.  The  comparative  absence  of  slip 
bands  is  interesting. 

Fig.  167  is  reproduced  from  the  tension  side  of  the  same  piece 
and  shows  well  developed  bands.  In  some  grains  two  sys- 
tems of  bands  are  seen  due  to  slip  along  two  directions.  The 
fact  that  the  adjacent  grains  are  not  separated  even  under 
heavy  strain  shows  the  strength  and  ductility  of  the  amor- 
phous boundary. 

Fig.  168,  taken  from  a  piece  loaded  in  pure  compression, 
shows  that  the  structure  of  Fig.  166  is  not  always  characteristic 

Plastic  Deformation 


of  this  type  of  loading  and  also  shows  plainly  two  systems  of 
slip  bands  in  practically  every  grain.  In  all  of  these  photo- 
mi'crographs,  note  that  the  direction  of  slip  is  constant  in  any 
given  grain,  but  is  not  usually  the  same  in  adjacent  grains.  The 
direction  of  slip  has  no  direct  relation  to  the  direction  of  the 
stress  but  is  determined  by  the  direction  of  the  crystallographic 
axis  of  the  ultra  microscopic  crystals  making  up  the  individual 

Figs.  169  and  170  show  the  distortion  of  grains  in  compres- 

Fig.  168. — Slip  bands  due  to  plastic  compression  in  malleable  iron 
Nitric  acid  etch  500  diameters 

sion  as  seen  on  a  polished  section  parallel  to  the  direction  of 
stress  prepared  after  the  distortion  has  occurred.  The  grains 
are  much  flattened  as  are  the  nodules  of  temper  carbon.  The 
grain  boundaries  are  nearly  obliterated  but  there  is  no  separation 
of  the  adjacent  grains.  The  effect  is  more  strongly  marked 
at  the  axis  of  the  specimen  than  near  the  surface  due  to  the 
fact  that  the  barreling  out  of  the  specimen  has  permitted  part 
of  the  reduction  in  height  to  be  made  by  bending  the  outer 
fibers  instead  of  upsetting  them.  The  specimen  from  which  these 
illustrations  were  made  was  compressed  to  a  little  less,  than 
one-half  of  its  original  height. 

The  effects  of  plastic  deformation  upon  the  grain  structure 
can  be  destroyed  by  somewhat  prolonged  heat  treatment  below 
the  critical  point.  By  such  treatment  a  new  series  of  equi-axed 


American   Malleable   Cast  Iron 

Fig.  169. — Plastic  deformation  of  malleable  in  compression 
Nitric  acid  etch  100  diameters 

Field  near  axis  of  the  specimen  in  a  plane  parallel  to  the  stress.     Note  the  flattening 
of  ferrite  grains,   faint  grain   boundaries  and  distortion  of   temper   carbon 

grains  is  formed,  whose  size  depends  upon  the  degree  of  the 
previous  plastic  deformation  and  the  heat  treatment  adopted. 
Fig.  172  shows  an  axial  section  of  a  specimen  similar  to  that  shown 
in  Fig.  169,  after  about  five  hours  at  650  degrees  Cent.  While 
the  ferrite  becomes  equi-axed  and  fine  grained  the  deformation 
of  the  temper  carbon  still  persists. 

Path  of  Rupture  Shown 

Fig.  171  shows  the  path  of  rupture  of  malleable  broken  in 
cross  bending.  It  was  prepared  by  breaking  a  wedge-shaped 
piece  by  bending  it  over  until  fracture  occurred.  The  fracture 
was  then  plated  with  copper,  the  specimen  sawed  in  two  at 
right  angles  to  the  ruptured  surface  and  parallel  to  the  cross 
bending  stress  and  the  exposed  surface  polished. 

Plastic  Deformation 


Fig.   170. — Same   specimen  as   shown  in   Fig.    169 

Nitric  acid  etch  100  diameters 

Field  near  surface  of  specimen   in  plane  parallel   to  stress.      Note  the  difference   from 

Fig.  169  in  lessened  intensity  of  all  changes 

It  is  particularly  interesting  to  note  how  the  path  of  rupture 
goes  far  out  of  its  way  to  include  temper  carbon  nodules.  This 
makes  many  deep  depressions  in  the  broken  surface  and  due  to 
the  shadows  in  the  bottom  of  these  depressions  produces  the 
characteristic  black  fracture  of  the  product.  It  is  not  often 
recognized  that  the  presence  of  temper  carbon  is  not  a  suffi- 
cient explanation  of  the  black  fracture  -for  this  material,  rep- 
resenting about  6  per  cent  of  an  average  cross  section,  would 
not  be  nearly  sufficient  to  darken  the  surrounding  silver  white 

It  is  only  due  to  the  fact  that  the  plane  of  rupture  takes 
in  many  more  nodules  of  carbon  than  would  be  found  in  an 
average  section  and  in  so  doing  produces  a  ,sort  of  "nap"  that 


American  Malleable  Cast  Iron 

o    c  ^, 

3     <u  In 


£    CJ    £3 

03        r^ 

uT   CTj 

8  -3 

a  3 

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t    fl  § 

be      — 


&  H 

Plastic  Deformation 


the  fracture  appears  as  dark  as  it  does.  A  fracture  running 
at  random  along  grain  boundaries  would  be  steely  and  crystalline 
in  character. 

The  mechanical  effects  of  plastic  deformation  offer  a  most 
interesting  field  of  investigation.  Most  engineers  are  acquainted 
with  the  effects  produced  by  cold  rolling  on  steel  and  brass  rods 
and  sheets,  and  by  cold  drawing  on  copper  and  iron  wires ;  the 

Fig.    172. — Malleable  iron  compressed  about  one-half.    Annealed   5   hours 

at    650    degrees    Cent. 

hardening  is   a   consequence   of    the    distortion   of    the   metallic 

Beilby's  theory  suggests  that  the  change  in  properties  is  caused 
by  formation  of  amorphous  iron  due  to  the  partial  destruction  of 
the  normal  crystal  structure  when  this  becomes  distorted.  In 
this  view  the  greater  the  coldwork  the  more  nearly  does  the  ma- 
terial as  a  whole  assume  the  properties  of  this  noncrystalline 
iron,  Jeffries  and  Archer  have  dealt  ably  with  the  relation  be- 
tween slip  and  hardness  in  an  article  appearing  on  page  1057 

350 • American   Malleable   Cast  Iron __ 

of  the  June  15,  1921  issue  of  Chemical  and  Metallurgical  En- 

For  the  purpose  of  the  present  study  we  may  dismiss  from 
consideration  the  more  abstruse  theoretical  considerations  and 
assume  it  to  be  an  experimentally  determined  fact  that  metal 
which  has  suffered  plastic  deformation  has  become  permanently 
altered  as  to  its  physical  properties. 

As  a  matter  of  fact  this  premise  is  of  far  reaching  effect. 
Although  it  is  becoming  more  and  more  usual  to  base  engineer- 
ing design  upon  the  elastic  limit  rather  than  upon  ultimate 
strength,  still  there  always  remains  the  possibility  that  a  struc- 
tural detail  will  be  subjected,  during  manufacture  or  in  use,  to 
stresses  which  although  insufficient  to  produce  rupture  will 
produce  plastic  deformation  and  the  accompanying  changes  in 
physical  properties. 

In  utilizing  a  given  specimen  of  a  ductile  metal  we  must 
consider  not  only  the  normal  physical  properties  of  that  metal 
but  its  entire  previous  history  with  respect  to  applied  stress 
and  also  its  subsequent  service  in  so  far  as  that  is  predictable. 

In  the  case  of  pure  iron  chemical  means  are  available  for  de- 
tecting the  presence  of  plastic  deformation.  The  products  of 
the  reaction  between  nitric  acid  and  unstrained  iron  differ  from 
those  if  the  iron  has  suffered  strain.  An  analysis  of  the  reaction 
products  thus  will  permit  of  conclusions  as  to  the  conditions  of 
the  metal.  The  method  has  not  yet  been  applied  to  malleable 
owing  to  the  disturbing  effect  of  the  residue  of  graphitic  car- 

We  might  assure  ourselves  of  the  absence  of  cold  work  by 
a  heat  treatment  just,  before  use  but  this  is  impracticable.  For 
the  purpose  of  the  designer  and  manufacturer  we  must  assume 
that  the  behavior  of  any  ductile  material  in  service  involves  each 
stress  applied  in  its  previous  history  and  not  single  stresses. 

It  is  possible  that  the  entire  problem  is  so  complex  that  a 
clear  understanding  of  the  effects  of  sequences  of  stress  is  be- 
yond our  grasp.  Four  cases  can  be  distinguished: 

1.     The  stresses  in  the  sequence  differ  neither  in  character, 

Plastic  Deformation  351 

magnitude  or  sign.     This  may  be  illustrated  by  a  load  which  is 
alternately  applied  and  removed. 

2.  The  stresses  do  not  differ  in  character  or  sign,  but  differ 
in  magnitude.     A  load  that  is  constantly  applied  but  varies  in 
intensity  is  an  example. 

3.  The  stresses  do  not  vary  in  character  but  vary  in  mag- 
nitude and  algebraic  sign.     Such  a  condition  could  be  caused  by 
alternate  compression  and  tension,  crossbending  in  opposite  direc- 
tions as  in  rotating  beam  test,  torque  in  opposite  directions  etc. 

4.  The  stresses  vary  with  respect  to  all  three  characteristics. 
This  would  be  the  case  if  torque  were  followed  or  preceded  by 
tension  or  compression  or  if  compression  in  one  direction  were 
followed  by  tension  or  compression  at  right  angles  thereto,  etc. 

The  ever  increasing  complexity  possible  will  be  readily  ob- 
served. To  this  complexity  must  be  added  the  fact  that  ac- 
cording to  Nutting's  conclusions  the  stress  under  plastic  deforma- 
tion is  a  function  of  the  time  of  application. 

A  formal  study  of  the  entire  phenomenon  therefore  is 
scarcely  possible  by  any  individual  or  laboratory;  indeed  the 
vast  amount  of  work  which  has  been  done  in  impact  and  fatigue 
testing  has  but  incompletely  studied  a  small  portion  of  this  im- 
mense field. 

New  Data  Is  Available 

It  is  therefore  with  humility  that  the  author  ventures  to 
record  certain  observations,  not  much  better  than  qualitative  in 
character,  on  some  of  the  mechanical  effects  of  plastic  deforma- 
tion of  malleable.  According  to  the  Nutting  formula  the  strain 
under  plastic  flow  is  proportional  to  a  higher  power  than  unity 
of  the  applied  stress  and  to  a  fractional  power  of  the  time  of 

Up  to  the  proportional  limit,  the  deformation  is  elastic  and 
proportional  to  the  stress.  The  exponent  of  the  stress  is  unity 
and  not  greater  than  unity  and  the  strain  does  not  depend  upon 
time.  The  exponent  of  time  is  zero.  The  course  of  the  usual 
stress  strain  diagram,  in  tension,  for  malleable  seems  to  in- 
dicate that,  for  rather  quickly  increasing  stresses  the  plastic 
deformation  of  malleable  is  approximately  proportional  to  the 
sixth  power  of  the  applied  stress.  There  is  a  surprisingly 


/Inter lean   Malleable   Cast   Iron 

Slow  Is  At  The  Rote  Of  .0000157  Per  Minute 
FasMsM  Thetfate  Of  .Ob"  Per  Minute 

.02        .04        .06        .08        .10         .12         .14        .16         .18        .20        .22 
fc"0       .0004     .0008    .0012      0016     .0020     .0024     .0028    .0031    .0036     .0040    .0044     .0046 


Fig.    173. — Stress    strain    diagram  .of    malleable    iron    in    tension    for    two 

rates  of  loading 

short  transition  range  between  the  point  where  the  strain  is 
directly  proportional  to  the  stress  and  the  point  where  it  begins 
to  be  proportional  to  the  sixth  power. 

Stress    Exponent    Changes 

During  the  transition  range  the  exponent  of  stress  obviously 
changes  progressively  from  1  to  6.  To  illustrate  the  effect  of 
time  on  plastic  deformation  two  stress  strain  diagrams  are 
shown  in  Fig.  173.  In  one  of  these  the  diagram  was  made  rapidly 
as  extensometer  readings  could  be  taken  while  in  the  other  each 
increment  of  load  was  maintained  till  no  further  increment  of 
length  was  observed.  In  the  former  case  the  time  was  perhaps 
four  or  five  minutes ;  in  the  latter  case  it  was  250  hours. 

It  is  obvious  that  if  quickly  loaded,  to  moderate  stress, 
the  metal  will  be  stiff er  than  if  the  stress  must  be  endured  in- 
definitely. The  ultimate  strength  and  elongation  are  unaffected 
however.  In  Fig.  174  is  shown  the  progress  of  deformation 

Plastic  Deformation 


with  time  at  two  intensities  of  stress,  in  each  case  the  last  500 
pounds  increment  of  load  having  been  applied  only  after  equili- 
brium had  been  attained  under  the  previous  load.  In  Fig.  175 
a  similar  graph  is  plotted  for  behavior  under  a  quickly  applied 
load  well  above  the  yield  point.  Below  the  proportional  limit 
no  increment  of  strain  with  time  is  observed  stress  being 

Having   thus    given    concrete    examples    of    the    application 
of  the  Nutting  hypothesis  to  this  particular  metal  we  may  turn 

£8,500  Lb5.  Per  5o.  In. 

29,500  Lb5.  Per  So. 

Chances  of  Strain  with  Time 
at  Small  Increment  of  Stress 

0      .001     .002,  .003    .004   .005    .006  .007   .008  .009   .010    .Oil 

Elongation  in  Inches  Over  6" 

Fig.    174. — Changes   of  strain   with  time  at   small   increment   of  stress 


American   Malleable   Cast  Iron* 

to  the  effect  of  previous  tensile  stresses  to  the  stress-strain  re- 
lationships during  subsequent  stresses  of  the  same  character. 

It  is  well  known  that  a  material  to  which  a  tensile  strength 
in  excess  of  the  elastic  limit  has  been  applied,  thereafter  has 
an  elastic  limit  equal  to  the  previous  load.  The  stress-strain 
diagram  under  successive  increasing  tensile  stress  is  shown  in 
Fig.  176.  It  will  be  seen  that  up  to  the  proportional  limit  the 
stress  leaves  no  permanent  effect.  On  releasing  a  stress  which 


Curve  15  Ap 






10      IE       14      16       18      SO      11      £4 
Time  in  Hours 


Fig.   175. — Changes   of   strain  with  time  under  considerable   increment   of 
stress   (about  70  per  cent  of  ultimate  strength) 

has  produced  plastic  deformation  the  material  contracts  elastic- 
ally,  retaining  a  permanent  set.  Under  a  subsequent  load  it 
stretches  elastically  up  to  the  previous  maximum  and  then  be- 
yond that  deforms  according  to  a  typical  plastic  deformation 

A  similar  cycle  is  repeated  for  each  subsequent  load,  pro- 
vided the  previous  load  is  exceeded.  If  not,  then  the  metal 
merely  deforms  elastically.  A  corollary  seems  to  be  that  no 
work  is  absorbed  by  the  metal  except  during  the  plastic  defor- 
mation, hence  it  is  difficult  to  see  how  the  material  could  fail 

Plastic  Deformation 


in  fatigue  by  repetitions  of  any  tensile  stress  which  is  of  suf- 
ficient intensity  to  cause  rupture  on  its  first  application.  Dalby 
finds  that  although  the  speciman  appears  perfectly  elastic  on 
successive  loadings  actually  no  part  of  the  curve  on  unloading 
or  reloading  is  a  straight  line  but  the  two  form  a  series  of 
loops  one  for  each  repetition  which  of  course  amount  to  an  ab- 


25.000  13 


c?  •,5 

>  train  D/aqromOrnalle 





Iron  In  Repeated  Tension  Under^. 




Increasing  Lood5 

















ZO  000  c/) 









t—  i 

17.500  §> 
15  000  Q. 


12500  ^ 



7500  ^ 

5000  S- 











O  2500 









—  I 








































0       001     .002     003    .004      005    .006     .007    006    .009     010     011      012     .015 

ClongoTion  In  fight  Inches 

Fig.    176. — Stress    strain   diagram   of    malleable    iron    in    repeated   tension 
under  increasing  loads 

sorption  of  energy.  Similar  loops  can  be  observed  in  malleable 
if  the  magnification  be  sufficient.  They  are  barely  visible  in 
the  diagram. 

The  simplest  case  of  stress  reversing  in  algebraic  sign  is  that 
alternating  between  tension  and  compression  of  equal  intensity 
although  alternate  torsional  shear  is  also  of  considerable  im- 
portance. We  have  seen  in  the  earlier  chapters  of  this  series 
that  the  behavior,  at  least  within  the  elastic  limit,  of  malleable 

356 American   Malleable   Cast   Iron 

in  tension  and  compression,  is  similar;  the  proportional  limit, 
being  about  15,000  pounds  per  square  inch  and  the  modulus 
of  elasticity  about  25  x  106  pounds  per  square  inch.  Thus  there 
is  an  elastic  range  of  about  30,000  pounds  per  square  inch, 
one  half  on  each  side  of  the  neutral  or  unloaded  condition 
through  which  the  intensity  of  stress  can  be  varied  without 
plastic  deformation. 

Applying  Alternate  Tension  and  Compression 
One  of  the  simplest  experimental  methods  of  applying 
alternate  tension  and  compression  to  a  specimen  is  that  of 
bending  a  beam  to  and  fro  in  opposite  directions.  The  be- 
havior of  malleable  under  cross  bending  stresses  has  already 
been  fully  considered,  notably  the  fact  that  ultimate  strength 
and  elastic  limit  determined  in  this  manner  bear  no  direct  re- 
lation to  these  constants  as  determined  in  pure  tension  and  com- 
pression. The  explanation  of  this  observation  has  also  been 

The  graph  in  Fig.  176  indicates  the  response  of  a  malleable 
beam  nominally  J/£ -inch' wide  and  1-inch  deep  on  supports  10- 
inches  apart  to  alternations  of  stress.  The  deflections  are  plot- 
ted against  apparent  maximum  fibre  stress,  as  calculated  from 
the  known  dimensions  of  the  specimen  and  the  applied  load. 
When  as  the  apparent  proportional  limit  is  not  exceeded,  the 
stress-strain  diagram  under  this  cyclic  cross  bending  is  merely 
a  straight  line  through  the  origin  at  an  angle  depending  upon 
the  modulus  of  elasticity  o£  the  metal.  However,,  when  the 
load  in  either  direction  exceeds  the  proportional  limit  the  stress 
strain  diagram  becomes  a  curve,  plastic  deformation  taking 
iplace.  As  the  specimen  is  unloaded  the  elastic  deformation 
alone  is  removed  and  at  zero  a  certain  permanent  set  equal 
to  the  plastic  deformation  remains. 

Elastic  Limit  Increases 

The  effect  of  this  plastic  deformation  is  represented  not 
only  by  the  measurable  permanent  set  but  also  by  the  increased 
elastic  limit  in  the  direction  of  the  previously  applied  load. 
On  reversing  the  direction  of  stress  the  elastic  limit  is  en- 
countered sooner  than  it  should  be  and  the  plastic  deformation 

Plastic  Deformation 


begins  at  a  lower  stress   than  was   the  case   in   the  unstrained 

When  an  intensity  of  stress  equal. to  the  previous  maximum 
but  of  opposite  sign  is  attained  in  a  perfectly  homogeneous 
specimen,  an  equal  and  opposite  strain  would  ensue  although 
in  the  present  case  the  negative  deflections  all  seem  somewhat 

•°?»25     50      37.5     W       l£5      0       12.5     £5      57.9     50      62.5" 
6tre55ln  Thousand  Pounds  Per  SOuare  Inch 

Fig.   177. —  Behavior  of  malleable  under  cyclic  bending  under  increas- 
ing  loads 

less  than  the  corresponding  positive  ones. 

Action  of  Specimen 

On  unloading  the  specimen  it  straightens  out  first  elas- 
tically,  retaining  a  negative  set  at  zero  load.  Under  reversed 
loads  it  finally  .deforms  plastically  until  at  the  stress  corres- 
ponding to  the  first  (positive  maximum)  it  has  the  original 


American  Malleable   Cast  Iron 

Thus  the  cyclic  cross  bending  stress-strain  diagram  is  a 
spindle  shaped  loop  whose  area  represent?  the  work  done1  in 
plastic  deformation.  Plastic  deformation  in  a  given  direction 
raises  the  elastic  limit  in  that  direction  and  decreases  the  abso- 
lute value  of  this  constant  in  the  opposite  direction,  the  elastic 
range  remaining  approximately  constant.  With  successively 
increasing  intensities  of  stress  the  area  of  this  mechanical 
hystersis  loop  grows  larger  and  larger  as  shown  in  Fig.  177. 

If  instead  of  applying  cyclic  cross  bending  in  a  manner  so 
that  each  cycle  oscillates  through  a  wider  range  of  stress  than 
the  preceding  one  we  merely  repeat  a  given  cycle  indefinitely, 
it  is  found  that  the  hysteresis  loop  decreases  in  area  with  suc- 
cessive cycles.  Fig.  178  shows  the  first  and  tenth  loops  of  such 


bl.5      50       37.5       25        125        0         12-5       £5       315       50       625 

Stress  In  Thousand  Pounds  Per  Square  IncH 

Fig.    178. — Behavior  of   malleable   under   cyclic   cross   bending   at   constant 

maximum  stress 

Plastic  Deformation 



Maximum  Deflection 

2,345        6        789 
No.  of  Applications 

Fig.  179. — Maximum  deflection  and  permanent  set  under  cyclic  cross  bend- 
ing at  constant  maximum  stress 

a  series.  The  decrease  in  work  per  cycle  is  due  to  the  smaller 
plastic  deformation  in  each  successive  cycle  due  to  the  hardening 
of  the  metal  from  the  cumulative  effect  of  all  the  slip  produced. 
The  decrease  in  deflection  and  permanent  set  is  not  at  constant 
rate  but  decreases  with  each  successive  loading  as  shown  in  Fig. 
179  and  approaches  a  fixed  minimum  of  finite  size.  The  deflections 
and  sets  are  shown  to  be  different  according  to  which  half  the 
specimen  is  in  tension.  This  is  presumably  due  to  lack  of  com- 
plete symmetry  about  the  neutral  axis.  The  work  done  by  a 
great  number  of  such  alternations  will  finally  rupture  the  speci- 
men. This  constitutes  the  phenomenon  of  fatigue.  The  phe- 
nomenon of  fatigue  of  metals  so  far  as  it  is  known  has  been 
discussed  in  another  chapter.  The  experiments  just  re- 
corded having  shown  the  approximate  extent  to  which  tensile 
or  compressive  loads  strengthen  the  material  for  subsequent  loads 

360  American  Malleable   Cast   Iron 

in  the  same  direction  and  weaken  it  for  loads  of  opposite  sign. 
From  these  experiments  we  can  gain  at  least  a  qualitative  insight 
upon  the  effect  of  a  previous  cross  bending  upon  subsequent 
tension  or  compression  in  a  direction  parallel  to  the  length  of 
the  specimen  and  vice,  versa.  The  quantitative  interpretation  is 
impractical — perhaps  impossible — owing  to  the  difficulty  of  ac- 
counting for  the  distribution  of  stress  in  a  plastically  strained 

Behavior  of  Specimen 

Consequently  under  the  subsequently  applied  longitudinal 
stress  the  elastic  limit  will  be  first  exceeded  on  that  edge  of  the 
specimen  which  is  experiencing  a  reversal  of  stress.  As  the 
applied  longitudinal  load  is  increased  a  greater  and  greater  por- 
tion of  the  area  experiences  plastic  deformation  until  finally  the 
elastic  limit  also  is  reached  at  the  opposite  edge. 

At  intermediate  intensities  of  stress  in  a  portion  of  the  spe- 
cimen elastic  strain  exists,  in  another  portion  plastic  strain.  From 
the  nature  of  the  case  the  ratio  of  strain  to  stress  is  greater  for 
plastic  than  elastic  deformation.  The  side  experiencing  a  re- 
versal of  stress  will  stretch  or  compress  more  rapidly  and  an 
eccentricity  of  loading  will  result  from  the  unequal  strain  dis- 
tribution. Such  an  eccentricity  in  the  case  of  compression  will 
result  in  the  superposition  of  a  bending  moment  on  the  longi- 
tudinal stress,  as  in  the  case  of  columns  which  are  eccentrically 
loaded  and  a  given  load  will  produce  far  greater  unit  stresses 
than  might  be  expected. 

In  the  case  of  tension  the  eccentricity  of  loading  will  re- 
sult in  the  transfer  of  a  disproportionate  amount  of  load  to  a  few 
of  the  stiffer  fibers  with  an  accompanying  high  unit  stress. 

Conversely  the  effect  of  a  previous  longitudinal  stress  upon 
subsequent  cross  bending  loads  is  to  shift  the  neutral  axis  to- 
ward that  surface  of  the  specimen  which  is  being  stressed  in  the 
same  sense  as  the  first  load.  This  shift  goes  on  until  the 
moment  of  resistance  of  the  portion  of  the  specimens  in  opposite 
sides  of  the  axis  about  the  axis  are  equal. 

The  sum  of  the  two  moments,  constituting  the  moment  of 
resistance  is  thereby  decreased.  In  either  event,  although  we 
may  not  be  able  to  solve  numerically  the  complex  mechanics  we 

Plastic  Deformation  361 

may  draw   the   conclusion  that  cross  bending  weakens   the  ma- 
terial for  subsequent  tension  or  compression  and  vice  versa. 

The  practical  application  of  this  conclusion  is  that  a  detail 
which  in  fabrication  has  been  subjected  to  severe  cold  work 
cannot  be  expected  to  be  as  strong  under  loadings  involving  a 
reversal  of  the  stress  previously  encountered  as  unworked  metal 
would  be.  This  conclusion  applies  equally  to  all  ductile  materials 
and  should  serve  as  a  warning  against  needlessly  energetic 
straightening  or  beading  operations.  Many  malleable  castings 
are  cast  to  a  simpler  form  than  intended  and  then  bent  to  the 
more  complex  shapes  demanded.  Air  brake  hose  clamps  are 
examples  of  this  practice.  Such  parts  will  never  develop  the 
full  strength  of  the  original  metal. 

In  all  the  preceding  cases  the  loadings  have  been  such  as 
to  set  up  strains  parallel  to  the  subsequent  stresses.  A  variety 
of  circumstances  are  possible  in  which  the  final  load  has  no 
component  parallel  to  that  producing  the  plastic  deformation. 

Two  typical  cases  are  torsional  shear  followed  by  tension 
and  compression  followed  by  tension  or  compression  in  a  di- 
rection normal  to  the  first  compression.  Compression  followed 
by  a  cross  bending  load  parallel  to  the  direction  of  compression 
is,  of  course,  a  special  case  of  the  preceding  involving  both 
tension  and  compression. 

The  combination  of  compression  followed  by  tension,  com- 
pression, or  both,  normal  to  the  original  strain  is  the  condition 
which  may  arise  where  a  piece  is  reduced  to  the  desired  dimen- 
sions by  compression  in  a  press  rather  than  by  machining.  In 
Fig.  180  are  shown  two  stress-strain  diagrams  on  specimens 
nominally  ^>-inch  square  subjected  to  cross  bending  load  on 
supports  10  inches  apart.  One  specimen,  A,  is  of  normal  metal 
in  its  original  condition,  while  the  other,  C,  was  produced  from 
a  thicker  bar  by  compressing  it  to  a  final  depth  of  J/£  inch. 
The  compressed  dimension  is  vertical,  that  is,  parallel  to  the 
direction  of  the  load  in  the  final  test.  The  effect  of  relatively 
heavy  compression  under  these  circumstances  can  be  learned  by 
a  comparison  of  the  two  graphs. 

A  few  scattering  tests  of  the  effect  of  shear  upon  subse- 
quent tensile  stress  have  been  made. 


American  Malleable   Cast  Iron 

In  Fig.  180  certain  tests  of  this  character  are  tabulated. 
Standard  A.  S.  T.  M.  tension  specimens  were  twisted  through 
various  angles  and  then  broken  in  tension.  In  the  illustration  the 
angle  of  twist  under  load  is  plotted  against  the  tensile  properties 
of  the  resulting  metal. 

It  will  be  noted  that  a  rapid  and  continuous  decrease  in 
elongation  is  encountered  with  increasing  torsional  deformation. 
The  tensile  strength  first  rises  rapidly  to  a  maximum  and  then 
decreases  still  more  rapidly.  The  location*  of  the  maximum 

Load  In  Pounds  Ai  Center 



»  - 






Stress  Deflection  Dioqram  Of 
Malleable  Iron  InCro55  Bend  nq  With 
And  Without  Previous  Cold  Work  ^ 







_  * 


































,  ^ 































0        JOl        .01        .OS        .04        .05        Ob         07       .00 


.09         .10          .11         .12         .15         .14-          15          .6 


Fig.    180. — Stress   deflection   diagram   of   malleable    in   cross   bending   with 
and  without  previous  cold  work 

tensile  strength  corresponds  approximately  to  the  torsional  yield 
point,  as  may  be  seen  from  the  torsional  stress  strain  diagram. 
The  curve  suggests  a  hardening  of  the  metal  due  to  the  forma- 
tion of  amorphous  metal  followed  at  higher  strains  by  disrup- 
tion at  the  grain  boundaries. 

Failure  in  tension  after  great  torsional  strain  did  not  result 
approximately  normal  to  the  axis  but  in  a  spiral  surface  ap- 
proximately normal  to  the  helix  angle  into  which  the  originally 
straight  elements  of  the  specimen  have  been  strained.  There  is 
a  suggestion  here  that  distortion  is  not  due  to  pure  shear. 

We  have  considered  the  effect  of  a  series  of  stresses  of 
known  intensity  and  direction  upon  a  ductile  material.  Another 

Plastic  Deformation 


important  condition  is  that  in  which,  instead  of  a  series  of 
known  stresses  the  specimen  is  required  to  undergo  a  series  of 
known  increments  of  energy. 

Impact  testing  by  a  series     of  equal  or  increasing  blows, 
is  the  principal  application  of  this  type  of  plastic  deformation. 

90      180     £70    360    450    540    680    7EO    6)0     900    990     1080 
Angle  Of  Torsion  (Degrees)  In  4'  Goqe  Length 

Fig.  181. — Effect  of  torsional  deformation  upon  subsequent  tensile  strength 

of  malleable 

In  this  case  the  intensity  of  maximum  stress  is  a  function  both 
of  the  energy  input  of  the  blow  and  the  elastic  and  plastic  de- 
formation of  the  specimen.  The  latter  factor  depends  upon  the 
previous  plastic  deformation  of  the  specimen  and  hence  is  a 
function  of  the  magnitude  and  number  of  the  preceding  series 
of  inputs  of  energy. 


American   Malleable   Cast  Iron 

Since  malleable  is  often  subjected  to  repeated  impact  in  serv- 
ice and  occasionally  in  testing,  this  condition  is  of  special  im- 
portance in  connection  with  a  study  of  that  metal. 

If  the  load  deformation  curve  of  a  given  specimen  under 
plastice  deformation  were  capable  of  mathematical  definition  in 
terms  of  its  dimensions  and  properties  and  the  rate  of  applica- 
tion of  the  load,  a  mathematical  study  of  this  problem  would 
be  feasible  although  probably  quite  complex. 

However,  the  problem  may  be  simplified  by  assuming  that 


Fig.    182. — Absorption    of    energy    from    successive    impacts 

we  have  experimentally  determined  the  load-deformation  dia- 
gram of  a  given  specimen  under  given  conditions.  The  load- 
deformation  diagram  in  every  respect  is  similar  to  a  stress- 
strain  diagram  except  that  the  co-ordinates  are  actual  load 
and  actual  deflection  instead  of  unit  stress  and  unit  strain.  We 
can  conceive  that  for  a  given  specimen  such  a  graph  might  be 
autographically  produced  under  rates  of  application  of  load 
as  rapid  as  are  encountered  in  impact  testing. 

Referring  to  Fig.  182  let  OLU  represent  the  load-deforma- 
tion curve  described  above,  L  being  the  elastic  limit  and  U ,  the 
ultimate  strength  and  tan  0  the  modulus  of  elasticity.  Then  the 
energy  imparted  to  the  specimen  at  any  given  load  and  deforma- 
tion for  instance  is  the  area  below  the  curve  beginning  at  O 

Plastic  Deformation  365 

and  ending  at  an.  For  example,  OLa±a2  etc.,  anbn.  If  this  energy 
input  be  large  enough  the  point  an  will  then  reach  U,  the  energy 
being  the  represented  by  OLa^a2  etc.,  UV  and  this  energy  will 
produce  rupture  under  impact. 

Therefore,  if  impact  is  produced  by  a  single  blow,  the  en- 
ergy of  rupture  is  measured  by  the  entire  area  below  the  curve 
as  shown  above.  A  blow  having  an  energy  of  impact  of  OLM 
or  less  will  not  produce  a  plastic  deformation,  the  specimen  will 
return  to  its  original  form  after  the  load  is  removed  and  will 
have  absorbed  no  energy.  If  the  energy  of  impact  be  equal  to 
OLaJ)i  for  example,  when  the  load  is  removed  the  deformation 
will  decrease  along  a^  (parallel  to  OL)  and  a  permanent  set 
Oci  will  remain.  The  energy  OLa^c^  will  have  been  used  up 
in  plastic  deformation  and  the  elastic  limit  will  be  raised  to  a1 
and  the  deflection  at  the  elastic  limit  to  c-J)^.  The  new  load  de- 
flection curve  becomes  caa  etc.,  UV.  Thereafter  any  impact  of 
energy  not  greater  than  c^ajb^  will  produce  elastic  deformation 
only.  Suppose  the  second  impact  is  equal  to  C1a1a262  then  by 
similar  measuring  the  new  load  deflection  curve  becomes  C2a2a3an 
etc.,  UV  the  third  impact  moves  it  to  c3a4an  etc.,  UV  and  so  on, 
and  after  n  blows  it  becomes  cnan  UV  and  finally  perhaps  WUV 
in  which  case  a  blow  equal  to  or  greater  than  WUV  will  break 
the  specimen. 

Suppose  now  that  we  assume  an  equal  energy  input  with 
each  blow.  Then  OLaJb^  —  C1a1a2&2  =  C2a2a3b3  etc.,  — 
cn-1an-1an  bn.  It  is  obvious  by  inspection  that  up  to  the  point 
of  maximum  load  G  each  succeeding  one  of  the  similar  tri- 
angles caji,  C2a2b2  etc.,  is  of  larger  area  than  its  predecessor. 
These  triangles  represent  the  portion  of  the  energy  of  impact 
expended  on  elastic  deformation.  Consequently  a  smaller  per- 
centage of  the  constant  increment  of  energy  is  available  for 
plastic  deformation  with  each  succeeding  blow  up  to  that  pro- 
ducing maximum  deflection.  Beyond  this  point  an  inqreasing- 
ly  larger  amount  of  each  energy  increment  is  available  for  plastic 

Finally  if  ^c^a2c2  +  C2a2a3c3 — cn.^an  ^an  cn  etc.,  is  com- 
mensurate with  OLGUW  the  specimen  absorbs  on  the  last  blow 
energy  equivalent  to  UVW '. 

366  American  Malleable   Cast  Iron 

The  specimen  has  then  absorbed  plastically  the  energy 
OLGUV  which  it  would  have  absorbed  if  broken  by  a  single 
impact.  Since,  however,  the  area  Cn-^n^an  cn  is  always  less 
than  the  area  c,,.^,.^^  b»  the  energy  absorbed  by  the  metal 
at  each  blow  is  measurably  less  than  the  total  energy  of  im- 
pact, a  large  part  of  the  energy  of  impact  being  returned  by  the 
specimen  during  its  elastic  recovery. 

Obviously  since  there  is  a  definite  amount  of  energy  not  ab- 
sorbed by  the  specimen  at  each  blow  a  smaller  percentage  of  the 
energy  of  impact  is  absorbed  the  lighter  the  blow.  If  the  energy 
of  rupture  be  measured  by  the  aggregate  of  the  energy  of  the 
entire  number  of  blows  to  produce  rupture  this  sum  will  be 
higher  the  smaller  the  individual  blows.  Consequently  testing 
a  metal  by  successive  impacts  can  yield  quantitatively  compar- 
able results  when  all  the  specimens  are  identical  in  form  and 
quality  in  addition  to  the  constancy  of  the  hammer  blow.  Of 
course  this  condition  is  impracticable  of  attainment,  the  quality 
being  unknown  before  the  test. 

In  practice  this  means  that  only  carefully  prepared  speci- 
mens of  similar  material  are  capable  of  fairly  accurate  com- 
parison by  repeated  impact  test. 

One  or  two  further  conclusions  may  be  gained  from  the 
study  of  the  diagram.  Energy  equivalent  to  the  area  OLM 
is  absorbed  by  the  specimen  elastically.  The  material  will  with- 
stand an  indefinite  number  of  impacts  of  this  magnitude  with- 
out permanent  deformation. 

Were  a  similar  triangle  FGH  drawn  with  its  apex  at  G , 
this  area  will  represent  the  maximum  elastic  absorption  of 
energy  the  specimen  can  sustain  when  by  repeated  impact  the 
elastic  limit  has  been  raised  to  the  ultimate  strength.  Any 
increment  of  energy  less  than  this  will  never  fracture  the 
piece  but  will  produce  a  maximum  deflection  after  a  given 
number  of  blows  which  will  not  be  further  increased  by  further 
repetitions  of  the  impact. 

The  area  OLM— LM.  LM  tan  0=modulus  of  elasticity  X 
square  of  elastic  limit. 

The  area  FGH  =  GH.     CH  tan  0=modulus  of  elasticity 

Plastic  Deformation 


X   square  of  ultimate  strength. 

From  the  above  we  may  calculate  the  blows  required  to 
make  an  impact  test  workable  on  a  given  specimen. 

The  deflection  at  each  successive  blow  can  be  determined 
graphically  under  given  conditions  from  the  diagram.  An 
impact  test  in  which  the  energy  increment  increases  with  each 
blow  can  be  studied  in  a  similar  manner.  In  that  case  there  is 
no  possibility  of  coming  to  a  maximum  deflection  without  frac- 

Fig.   183. — Load  deformation  diagram  of.  specimen  subjected  to  alternate 


ture  for  the  increased  energy  of  the  succeeding  blow  would 
carry  the  deformation  beyond  G.  In  such  a  test  there  is  great 
danger  that  the  last  blow  will  be  equivalent  to  far  more  than  the 
energy  WUV  and  the  unabsorbed  energy  of  the  blow  will  be 
credited  also  to  the  specimen. 

We  may  generalize  to  the  effect  that  no  method  of  repeated 
impact  can  correctly  measure  the  energy  of  rupture  of  a  duc- 
tile metal.  In  a  similar  manner  we  may  study  graphically  the 

368  American   Malleable   Cast   Iron 

effect  of  alternate  impact  in  opposite  directions,  although  we 
may  be  confronted  with  the  difficulty  of  securing  the  necessary 
load  deformation  curves.  In  Fig.  183  U^L^OLU  is  the  original 
curve  for  the  specimen.  An  increment  of  energy  Oa^b^  de- 
forms it  to  a±  and  raises  the  elastic  limit  to  that  point.  The 
load-deformation  diagram  then  becomes  a-lO-lLLJJ'1^  and  an  in- 
crement of  energy  in  the  opposite  direction  to  the  first  OlL11a2b.2 
produces  a  load  of  a2b2  and  a  deformation  O^b^  The  new 
elastic  limit  becomes  a2  and  the  new  diagram  a2O2U2. 

The  next  increment  of  energy  is  diagramed  as  O2a3B3  and 
so  on.  It  will  be  seen  that  each  impact  in  one  direction  appar- 
ently decreases  both  the  ultimate  load  and  elongation  in  the  op- 
posite direction  an  expression  of  the  weakening  caused  by  a 
negative  plastic  deformation. 

In  the  absence  of  stress  strain  diagrams  under  dynamic 
loads  we  may  turn  as  the  best  available  substitute  to  the  vari- 
ous stress  strain  diagrams  given  throughout  these  chapters  and 
from  them  and  the  dknensions  of  the  specimens  estimate  the 
probable  load  deformation  curves  to  be  used. 

It  is  obvious  that  those  materials  in  which  the  elastic  limit 
is  quite  high  accompanied  by  a  high  elongation  are  these  which 
will  well  resist  repeated  impact.  The  high  elastic  limit  will  dissi- 
pate a  large  amount  of  energy  in  elastic  deformation  at  each 
blow  while  the  high  elongation  provides  a  large  amount  of  re- 
serve energy  for  plastic  deformation  before  rupture  takes  place. 

The  Young's  modulus  of  all  ferrous  materials  is  practically 
the  same,  hence  the  deformation  at  the  elastic  limit  is  in  direct 
proportion  to  the  elastic  limit.  In  steel  high  elastic  ratio  is  ob- 
tained only  at  the  expense  of  elongation  and  vice  versa.  The 
various  graphs  for  malleable,  indicating  a  constant  and  high 
elastic  ratio  and  an  elongation  increasing  with  strength  account 
for  its  excellent  behavior  under  repeated  impact  even  when  of 
sufficient  magnitude  to  produce  plastic  flow. 

In  this  connection,  incidentally  the  yield  point  of  metal 
is  the  governing  factor  in  ferrous  materials  for  the  small  reduc- 
tion in  the  area  representing  energy  clue  to  the  curvature  of 
the  stress-strain  diagram  between  the  proportional  limit  and 
yie!cl  point  is  negligible. 

Plastic  Deformation  369 

Plastic  deformation  has  been  discussed  mainly  because  of 
its  great  importance  in  the  utilization  of  malleable.  No  one 
realizes  more  than  the  author  the  unsatisfactory  state  of 
knowledge  and  the  lack  of  precise  numerical  data.  If  this 
chapter  has  enabled  the  reader  to  form  even  a  qualitative  image 
of  the  resistance  of  the  metal  above  the  elastic  limit  that  is  all 
that  can  be  expected.  An  infinite  amount  of  further  study  will 
be  required  before  concrete  mathematical  analyses  will  be 



WHILE  it  is  true  that  materials  of  construction  in  gen- 
eral are  used  to  resist  mechanical  stress,  yet  there  are 
service  conditions  when  other  properties,  such  as  ther- 
mal, chemical  or  electrical,   for  instance,  are  of  greater    conse- 

The  most  important  condition  of  this  kind  arises  in  the 
use  of  malleable  as  a  material  for  field  frames  of  electrical 
apparatus,  where  the  magnetic  characteristics  of  the  metal 
are  much  more  important  than  the  mechanical  strength.  It 
is  a  well  known  fact  that  if  a  coil  o£  wire  is  wound  around 
a  piece  of  iron  and  a  current  is  passed  through  the  coil,  the 
iron  becomes  magnetic.  This  property  of  iron,  which  it  shares 
in  a  very  limited  degree  with  a  few  other  metals,  is  of  im- 
portance in  electrical  machinery.  If  the  power  to  become 
magnetic  is  the  quality  desired,  evidently  the  metal  which  forms 
the  strongest  magnet  with  the  same  coil  and  current  is  the 
most  valuable.  Therefore  it  is  desirable  to  determine  the  de- 
gree to  which  a  given  material  possesses  this  valuable  property. 
Avoiding  a  discussion  of  the  electrical  principles  and  of  the 
mathematical  reasoning  involved  in  the  study  of  magnetism,  it 
is  sufficient  to  say  that  the  intensity  of  magnetization,  repre- 
sented by  the  symbol  Hf  and  expressed  in  gausses  (lines  per 
square  centimeter)  can  be  calculated  from  the  dimensions  of  a 
magnetizing  coil  and  measurement  of  the  current.  When  an 
iron  core  is  inserted  in  the  coil  it  will  be  found  that  the  inten- 
sity of  magnetic  field  is  much  greater  than  the  calculated  value 
H.  This  higher  value,  known  as  magnetic  induction,  is  sym- 
bolized as  B  and  is  measured  in  the  same  units  as  H.  The 
ratio  of  B  to  H,  that  is,  the  number  of  times  stronger  the 
magnet  is  with  the  iron  core  than  without  any  core,  using  the 
coil  only,  is  called  the  permeability  of  the  material  and  is  the 
variable  represented  by  the  Greek  letter  /*. 

It  is   further  found  that  the  value  of  /*  depends  not  only 

372'  American  Malleable   Cast   Iron 

upon  the  material  'being  used  but  also  on  the  value  of  H  at 
which  the  experiment  is  made.  In  general,  the  permeability 
of  a  material  first  increases  as  H  increases,  soon  reaches  a 
maximum  and  then  falls  off,  first  rapidly  and  then  more  and 
more  slowly. 

The  value  of  /*  for  an  indefinitely  strong  field  is  prob- 
ably 1  for  all  materials.  Owing  to  experimental  difficulties 
determinations  close  to  the  zero  value  of  B  are  not  very 
reliable.  The  behavior  of  a  magnetic  material  is  usually  repre- 
sented by  a  so-called  magnetization  or  "B-H"  curve  in  which 
the  value  of  H,  the  strength  of  the  magnetic  field,  is  plotted 
horizontally  and  the  magnetic  induction  in  the  iron,  B,,  which 
is  equal  to  v-H,  is  plotted  vertically.  The  fact  that  /*  is  vari- 
able, depending  on  B  and  hence  on  H,  gives  this  curve  a  gen- 
eral form  which  rises  from  the  origin  (H  =  0,  B  =0)  first 
ait  a  rapidly  increasing  rate  as  H  increases  and  then  more 
slowly  until  it  becomes  horizontal  when  H  is  infinite.  As  a 
matter  of  fact  the  curve  becomes  nearly  horizontal  fairly 
soon,  and  /the  "knee"  in  the  curve,  somewhat  resembling  the 
yield  point  in  a  tensile  stress  strain  diagram,  represents  practi- 
cally the  maximum  flux  density  which  can  be  attained  in  a 
given  metal.  This  value  varies  widely  in  different  metals  and 
is  quite  definite  in  each  metal  having  almost  the  significance  of 
a  physical  constant.  This  characteristic  for  malleable  iron  is 
shown  in  curve  A,  Fig.  184.  The  specimen  was  in  the  form  of  a 
closed  ring  about  6  inches  in  diameter  and  having  a  rectangular 
section  0.33-inch  thick  radially  and  0.9-inch  wide.  The  per- 


meability,  A*  =  — 

for  various  values  of  //based  on  the  data  for  the  ring  described 
above,  is  shown  in  curve  B.  The  values  of  /*  as  related  to  B 
are  plotted  in  curve  C. 

When  a  material  has  been  magnetized  and  the  magnetic 
field  H  is  then  reduced,  the  magnetic  induction  B  in  the 
iron  decreases  but  not  at  the  same  rate  as  it  increased  with 
increasing  values  of  H.  When  H  is  reduced  to  0  there  usually 
remains  a  considerable  magnetic  induction  and  it  is  only 

Thermal  and  Electrical  Properties 


after  H  has   reached  a  definite  value  in  the  opposite  direction 
to  that  first  developed  that  B  falls  to  0. 

This  lag  of  induction  behind  magnetizing   force  is  due  to 
hysteresis.     The  value  of   B   when  H  is  reduced  from  a  high 



CO  5000 


10  20  3  40 

H  in  C.G.  5.  Units 

Fig.    184. — Magnetization   and   permeability   curves   of   malleable   cast    iron 

value  to  0  is  called  residual  magnetism,  and  the  negative  value 
of  H  required  to  bring  B  to  0  is  called  the  coercive  force. 
It  is  quite  possible  to  plot  a  curve,  similar  to  a  B-H  curve 
beginning  with  a  fairly  high  value  of  H,  lowering  H  gradually 
to  0,  then  increasing  it  in  the  opposite  direction  until  a  nega- 
tive value  is  reached  equal  in  magnitude  to  the  original  posi- 
tive value,  then  back  through  0  to  the  starting  point.  Such  a 

374  American   Malleable   Cast  Iron 

curve  forms  a  closed  loop  of  distinctive  form  called  a  'hysteresis 
loop.  The  area  of  this  loop  represents  energy  consumed  in 
magnetizing  and  demagnetizing  the  specimen.  Materials  strong- 
ly retaining  their  magnetism,  and  therefore  suitable  for  per- 
manent magnets  have  a  larger  hysteresis  loop  due  to  great 
residual  magnetism  and  coercive  force.  Material  for  electro- 
magnets, especially  where  frequent  changes  in  magnitude  or 
sign  are  required  in  field  strength  have  the  opposite  characteris- 

This  energy  is  dissipated  as  heat,  either  in  raising  the  tem- 
perature of  the  iron  or  radiated  to  the  surroundings.  The 
loss  is  of  industrial  importance  for  service  involving  reversals 
of  magnetism  in  that  it  involves  a  waste  of  energy  and  may  re- 
sult in  inadmissably  high  temperatures  being  reached  in  the 
magnetic  circuit,  possibly  sufficient  to  destroy  the  insulation  on 
the  coils.  The  energy  is  lost  once  for  each  cycle  of  magnetiza- 
tion so  that  for  alternating  currents  the  loss  depends  on  the 

It  can  be  shown  mathematically  that  the  energy  dissipated 
per  cycle  of  magnetization  per  cubic  centimeter  of  metal  is 
the  area  of  the  hysteresis  loop  divided  by  471",  regard  being  had 
of  course  to  the  scale  to  which  B  and  //  are  plotted.  This 
value  is  necessarily  dependent  on  the  magnetic  induction  ob- 
tained. In  Fig.  185  a  condition  is  plotted  in  which  saturation 
has  practically  been  attained,  hence  calculations  based  on 
this  graph  would  give  the  energy  dissipated  by  a  complete 
cycle.  The  area  actually  corresponds  to  a  value  of  11,388 
ergs  per  cubic  centimeter  of  metal.  Cyclic  magnetization  of 
malleable  to  an  inductance  of  13,200  centimeter-gram-second 
units  by  the  usual  60-cycle  alternating  current  would  raise  the 
temperature  of  the  iron  a  little  over  2  degrees  Fahr.  per  minure, 
assuming  no  radiation  of  heat. 

Steinmetz  has  determined  empirically  that  the  work  done 
in  a  cycle  of  magnetization  on  any  given  material  is  approxi- 
mately proportional  to  the  highest  magnetic  induction,  B  reached 
(in  the  cycle  raised  to  a  power  between  1.66  and  1.70.  This 
formula  serves  to  derive  the  work  done  on  the  same  material 
by  cycles  ending  at  different  inductions.  Therefore,  the  uv«- 

Thermal  and  Electrical  Properties 

.  375 

/»  Current  in  Ampere^ 
n*  Number  of  Turn;, 


20  0        -  20 

Intensity      of      Magnetization,     H 


Fig.    185. — Magnetic   properties   of    malleable    cast    iron 

teresis  loss  on  any  given  material,  is  a  constant  times  J51-68 
when  B  is  the  maximum  induction  reached  in  the  cycle.  This 
constant  varies  with  different  materials  and  is  designated  by 
the  Greek  letter  ^.  Calculation  from  the  preceding  data  gives 
a  value  of  0.00136  for  Steinmetz's  constant. 

This  very  low  value  is  logically  due  to  the  fact  that  the 

376 American   Malleable   Cast  Iron 

bulk  of  a  malleable  casting  is  a  fairly  pure  ferrite  contaminated 
mainly  by  silicon  whose  presence  is  an  advantage  and  also  to 
the  fact  that  the  anneal  involves  a  heat  treatment  consistent 
with  the  very  softest  condition  of  ferrite  possible.  So  far,  the 
writer  knows  of  no  case  where  the  electrical  resistance  of  mal- 
leable is  of  commercial  importance.  It  has  been  roughly  deter- 
mined to  be  0.000044  ohm  per  centimeter  cube.  More  recent 
and  accurate  data  indicate  the  specific  resistance  to  be  0.0000295 
ohms  per  centimeter  cube.  A  part  of  this  descrepancy  no  doubt 
is  due  to  the  heterogenous  character  of  the  material.  The 
newer  value  however  is  much  more  reliable.  Presumably  the 
resistance  decreases  with  the  carbon  content. 

The  change  in  resistance  with  temperature  is  shown  in 
Fig.  186,  the  resistance  at  room  temperature  being  taken  as 

Where  metal  parts  are  exposed  to  weather  or  to  the  action 
of  water  or  steam,  circumstances  arise  in  which  the  resistance 
of  the  material  to  rusting  is  of  prime  importance.  This  is 
particularly  true  under  circumstances  which  preclude  the  use  of 
paint,  galvanizing  and  similar  means  for  protecting  the  metal. 

This  opens  up  the  moot  subject  of  corrosion  of  iron  and 
the  relative  merits  of  accelerated  tests  in  dilute  acid  as  com- 
pared with  service  tests.  All  commercial  iron  alloys,  except 
a  few  high-silicon  metals,  dissolve  in  acids  more  or  less  rapidly. 
While  not  at  the  same  rate  for  all  forms  of  iron  and  steel 
the  deterioration  is  rapid  enough  to  preclude  the  use  of  ordinary 
ferrous  materials  for  corrosion  resisting  services. 

A  great  many  acid  corrosion  tests  have  been  conducted  on 
malleable  but  the  results  are  hardly  applicable  to  the  present 
discussion.  It  is  generally  admitted  that  since  corrosion  is  an 
electrolytic  phenomenon,  the  more  nearly  homogeneous  a  metal 
is  the  better  it  will  resist  corrosive  action  either  of  the  elements 
or  of  acids,  salt  water,  etc. 

Manganese  sometimes  is  alleged  to  be  an  offender  in  start- 
ing corrosion.  The  surface  of  a  malleable  casting  is  always 
nearly  carbon  free;  it  contains  rather  small  amounts  of  man- 
ganese, less  than  any  material  except  wrought  and  ingot  iron. 
Silicon  is  supposed  to  dissolve  in  ferrite,  when  present  in  mod- 

Thermal  and  Electrical  Properties 


erate  amount.  It  would  appear  therefore  that  malleable  should 
resist  rusting  moderately  well.  This  general  conclusion  is 
borne  out  by  the  fact  that  malleable  has  been  used  for  many 
years  in  the  manufacture  of  pipe  fittings,  radiator  nipples,  etc., 
and  complaints  that  the  material  has  failed  by  rusting  are  very 

Resistance  at  Temperature  tr  Resistance  at  Room  Temp. 

o  o  b 



































100            200            300           400            500            600           TOO 
Degrees   Cent. 

Fig.    186. — Variation   of   electrical   resistance   of    malleable   cast    iron   with 


There  is  also  of  record  the  case  of  a  malleable  iron  harness 
part  which  was  found  in  excavating  for  a  foundation.  The 
circumstances  were  such  as  to  make  it  certain  that  the  article 
had  been  in  the  soil  over  40  years,  yet  it  had  suffered  buft  little 
injury  to  the  surface.  The  only  service  test  with  which  the 
writer  is  familiar  was  conducted  to  determine  the  relative  life  of 
malleable  and  steel  railway  tie  plates.  Plates  of  both  ma- 
terials were  laid  in  the  same  track  at  the  same  time.  When 

378  American  Malleable  Cast  Iron 

the  steel  plates  had  completely  rusted  away  the  malleable  plates 
were  still  practically  in  their  original  condition.  It  seems  rather 
doubt  full  whether  in  the  present  state  of  our  knowledge  any 
quantitative  method  exists  of  measuring  resistance  to  corrosion 
other  than  a  direct  comparison  under  the  conditions  expected 
in  practice. 

In  a  great  many  cases  mechanism  is  required  to  function 
under  temperature  conditions  either  abnormally  high  or  ab- 
normally low.  The  principles  to  which  malleable  owes  its 
properties  indicate  obviously  that  malleable  cannot  be  ex- 
posed to  temperatures  above  Ac^  even  momentarily,  without 
being  permanently  destroyed. 

The  question  of  its  use  at  high  temperature  cannot  be 
dismissed  merely  with  the  statement  that  it  should  never  be 
exposed,  even  momentarily  to  temperatures  higher  than  say 
1300  degrees  Fahr.  lest  by  chance  Ac±  be  overstepped  and  a 
permanent  change  be  produced  in  the  metal.  There  are  many 
cases  where  castings  are  to  be  used  at  temperatures  considerably 
below  the  danger  point  and  the  designer -must  guide  himself 
by  the  effect  of  temperature  on  the  properties  of  the  material. 
Even  so  simple  a  property  as  the  dimensions  of  a  casting  are 
affected  by  variations  of  temperature.  Experiments  by  the 
author  have  shown  that  if  L0  be  the  length  of  a  malleable  cast- 
ing at  0  degrees  Cent,  when  the  casting  is  raised  to  a  tem- 
perature of  t  degrees  Cent,  its  length  Lt  will  be  given  by  the 

Lt   =  L0    (1-KOQ0006   H- -0000000125   t2) 

Translating  into  terms  of  Fahrenheit  temperature  the  re- 
vised formula  becomes 

Lt=L32   [1+. 0000033   (/•— 32)+. 00000000385    (t— 32 )2] 

These  figures  are  somewhat  cumbersome.  For  engineering 
purposes  it  may  be  more  convenient  to  take  the  expansion  at 
various  'Fahrenheit  temperatures  in  per  cent  of  the  length  at 
75  degrees  Fahr.  from  the  graph,  Fig.  187.  It  is  to  be  noted 
that  the  change  in  size  of  large  castings  where  raised  to  mod- 
erately high  temperatures  is  quite  significant.  Thus  a  cast- 
ing 3  feet  long  when  raised  to  600  degrees  Fahr.  expands 
over  0.1  inch  which  may  be  very  important  where  clearances 

Thermal  and  Electrical  Properties 


are  to  be  allowed. 

The  author  is  not  aware  of  any  actual  or  experimental 
determinations  of  the  specific  heat  of  malleable  cast  iron.  Since 
the  material  is  a  mechanical  mixture  of  graphitic  carbon  and 
nearly  pure  iron  we  may  use  provisionally  data  calculated  from 
the  known  constants  of  the  two  elements. 

The   conductivity  of   a   metal   for   heat  represented   by  the 








*  Jj 



—  m 




tted  Curve  Plate  the  V 
•the  Equation  if=L0( 
where  L0-  Length  a 
Lf  -      »       » 
•pansion  Measured  '/ 
Percentage  of  Leng 

ilue  0. 


that  7 



t  +  O.OOL 
























)                   200                 400                600                 800                1000               1200 
Temperature,  dcg    Fanr 

Fig.   187. — Expansion  of  malleable    cast    iron 

symbol  k  is  defined  as  "the  quantity  of  heat,  in  small  calories 
transmitted  through  a  plate  1  centimeter  thick  per  square  centi- 
meter of  surface  when  the  difference  in  temperature  between 
the  faces  is  1  degree  Cent. 

The  heat  transmitted  through  a  plate  of  metal  varies  di- 
rectly as  its  area  and  as  the  difference  in  temperature  between 
the  faces  and  inversely  as  the  thickness. 

The  value  of   k   varies   slightly  with   the   temperature,   de- 


American  Malleable   Cast  Iron 

creasing  for  iron  and  increasing  for  carbon  as  the  temperature 
rises.  At  room  temperature  (17  or  18  degrees  Cent.)  the  values 
for  k  for  iron  and  graphite  are  .161  and  .037,  respectively. 
(Smithsonian  Physical  Tables,  1921.) 

At  that  temperature  malleable  cast  iron  of  2   per  cent  to 







Fig.  188. — Heat  transfer  from  machined  malleable  to  still  water  for  various 
temperature    differences 

total  carbon  should  have  a  value  of  k  between  .1578  and  .1585, 
depending  on  how  readily  heat  can  be  transmitted  from  car- 
bon to  iron  and  vice  versa. 

On  the  same  authority  for  the  interval  between  100  and 
720  degrees  Cent,  the  value  of  k  becomes  .202  for  iron,  .306 
for  graphite,  and  between  .198  and  .204  for  malleable  iron. 

The  values  are  higher  than  certain  approximate  experimental 
values  determined  in  the  author's  laboratory.  Malleable  heated 
above  A,  will  have  its  thermal  conductivity  permanently  de- 

Thermal  and  Electrical  Properties 381 

creased    since   this   constant   decreases   with   the   combined    car- 
bon content. 

The  specific  heat  of  a  substance  is  the  quantity  of  heat  in 
small  calories  to  raise  the  temperature  of  one  gram  1  degree 

Iron  at  37  degrees  Cent,  has  a  specific  heat  of  .1092  (loc. 
cit.)  and  graphite  at  11  degrees  Cent,  a  specific  heat  of  .160. 
As  a  mechanical  mixture  of  98  per  cent  iron  and  2  per  cent 
graphite  and  neglecting  corrections  for  a  change  of  specific  heat 
with  temperature,  the  specific  heat  of  malleable  at  room  tem- 
perature should  be  .1102.  The  value  probably  is  quite  accurate, 
since  cast  iron  of  about  3%.  per  cent  Cent,  has  a  specific 
heat  of  .1189,  The  specific  heat  rises  with  the  temperature. 

In  view  of  the  approximate  character  of  these  deductions 
and  of  their  intended  application  a  detailed  study  of  the  rela- 
tion between  temperature,  thermal  conductivity  and  specific  heat 
seems  "unwarranted. 

All  ferrous  metals  grow  softer  and  weaker  at  elevated 
temperatures.  Accordingly  it  becomes  important  to  know  the 
quantitative  effect  of  temperature  upon  strength  in  order  that 
where  very  high  temperatures  are  unavoidable,  due  allowance 
may  be  made  in  design  for  the  changed  physical  properties  at 
the  higher  tempera  Lures. 

Since  the  tensile  properties  can  be  more  definitely  measure.'l 
than  any  other,  studies  on  the  effect  of  temperature  on  strength 
have  usually  been  made  on  tensile  specimens.  The  author  has 
conducted  experiments  of  this  character  by  breaking  very  care- 
fully made  specimens  at  temperatures  from  — 80  to  1450  de- 
grees Fahr. 

The  data  up  to  1200  degrees  Fahr. — the  highest  commer- 
cially safe  temperature  to  provide  against  the  possibility  of 
heating  up  to  a  temperature  which  will  permanently  affect 
the  product — are  shown  in  Fig.  189.  It  will  be  seen  that  malle- 
able cast  iron  has  tensile  properties  equal  to  those  it  possesses 
at  room  temperature  at  all  temperatures  from — 100  to  800 
degrees  Fahr.  Above  900  degrees  the  strength  decreases  rapid- 
ly and  at  1200  degrees  the  maximum  allowable  temperature,  the 


American   Malleable   Cast  Iron 

metal  is  onfy  one-fifth  as  strong  as  at  room  temperatures.  Pre- 
sumably very  'similar  relationships  will  be  observed  under  other 
loads,  compression  cross  bending,  etc. 

Temperature  affects  the  magnetic  properties  of  iron.  For 
large  values  of  H,  B  decreases  as  the  temperature  increases; 
the  reverse  is  true  for  very  small  values  of  H.  The  effect 
of  the  temperatures  is  not  strongly  marked  at  room  tempera- 

-100     0  200  400  600  800  1000          1200 

Temperature  j    deg.  Fahr 

Fig.   189. — Effect  of  temperature  upon  tensile  properties  of  malleable 

tures  but  increases  rapidly  as' the  temperature  goes  beyond  1200 
degrees  Fahr.  Presumably  the  behavior  of  malleable  is  in  ac- 
cord with  these  principles.  Actual  measurements  are  lacking. 
The  specific  heat  of  malleable,  that  is  the  number  of  heat 
units  required  to  raise  a  given  weight  of  that  material  1  de- 
gree in  temperature  as  compared  with  the  heat  units  to  raise  an 
equal  weight  of  water  1  degree  varies  from  0.11  at  75  degrees 
to  0.165  at  800  degrees  Fahr.  The  intervening  curve  is  near- 
ly straight,  being  but  slightly  concave  upward.  The  values  are 
calculated  from  the  specific  heats  of  iron  and  carbon.  Malle- 
able, being  a  mechanical  mixture  of  these  two  elements,  can 
have  this  constant  calculated  in  that  way. 

As  the  name  implies,  the  thermal  conductivity  of  a  metal 

Thermal  and  Electrical  Properties 


is  the  rate  at  which  it  will  conduct  heat.  The  constant  is  de- 
fined in  terms  of  the  quantity  of  heat  conducted  per  unit  of 
time  through  a  cross  section  of  unit  area  of  a  slab  of  unit 
thickness  whose  opposite  sides  differ  by  unity  in  temperature. 
The  quantity  of  heat  conducted  varies  directly  as  the  area  of 
the  conductor  and  as  the  temperature  difference  between  its 
ends  and  inversely  as  its  length.  However  the  thermal  conduc- 








Fig.    190. — Thermal   conductivity   of    malleable   cast   iron 

tivity  is  not  constant  but  varies  with  the  temperature. 

It  will  be  seen  that  the  flow  of  heat  obeys  the  same  law 
as  the  flow  of  electric  current ;  indeed  in  a  given  metal  the  ratio 
of  thermal  to  electrical  conductivity  is  nearly  constant  at  all 

The  determination  of  thermal  conductivity  is  not  alto- 
gether easy  especially  at  high  temperatures  and  consequently 
data  on  this  constant  are  somewhat  infrequent  and  not  con- 

The  British  Aeronautical  Research  committee  gives  data 
on  an  annealed  gray  iron  (1.84  per  cent  silicon)  containing  very 
little  combined  carbon  but  much  free  carbon  as  determined  in 
the  National  physical  laboratory.  The  committee  determined 

384  American   Malleable   Cast  Iron 

the  conductivity  between  40  degrees  Cent,  and  various  tempera- 
tures up  to  700  degrees  Cent.  The  data,  translated  into  mean 
temperatures,  have  been  plotted  in  Fig.  190.  The  conductivity 
of  pure  iron  is  shown  for  comparison. 

Both  on  account  of  the  lower  carbon  content  and  the  geo- 
metric form  of  the  free  carbon,  malleable  should  have  a  higher 
conductivity  than  a  cast  iron  specimen,  but  a  lower  than  pure 

The  black  dots  in  Fig.  190  give  a  number  of  observations 
by  Dr.  Gorton  in  the  author's  laboratory,  by  Wilkes'  method. 
The  data,  while  made  as  carefully  as  possible,  have  not  always 
appeared  above  criticism.  From  the  mean  value  of  Gorton's 
data  the  conductivity  can  be  taken  as  near  .135  at  100  degrees 
-Cent.  The  conductivities  at  other  temperatures  have  been  cal- 
culated from  the  known  thermal  coefficients  of  electrical  re- 
sistance and  plotted  as  a  line  which  follows  very  well  the  gen- 
eral direction  of  our  observations.  From  these  facts  we  are 
led  to  believe  that  our  data  may  be  concordant  enough  to  have 
some  utility. 

The  density  of  malleable  cast  iron  is  occasionally  of  im- 
portance in  the  calculation  of  weights.  This  varies  as  does  the 
shrinkage  allowance  on  patterns,  with  the  composition  of  prod- 
uct. The  specific  gravity  of  malleable,  that  is,  the  ratio  of  its 
density  to  that  of  water  is  between  7.25  and  7.45  and  de- 
pends on  the  temperature  at  which  the  experiment  is  made. 
The  metal  made  to  pass  the  specifications  of  the  American 
Society  of  Testing  Materials  will  have  a  specific  gravity  of 
about  7.40.  The  "shrinkage  allowance"  referred  to  under  such 
circumstances  should  be  about  0.9  to  1  per  cent,  agreeing  rather 
well  with  the  usual  ^-inch  per  foot  used  by  patternmakers. 
It  should  be  noted  in  passing  that  the  differences  in  "shrink- 
age" between  metal  differing  in  carbon  content  is  actually  an- 

All  white  cast  iron  shrinks  very  nearly  the  same  amount 
in  cooling  from  the  molten  state  (*4-inch  per  foot)  but  iron 
high  in  carbon  increases  in  size  more  when  the  carbon  is  lib- 
erated than  those  low  in  that  element. 

Selected  Bibliography 


Chronology  of  -Iron  and  Steel,  by  Stephen  L.  Goodale,  Pittsburgh  Iron  & 
Steel  Foundries  Co.  (1920.)  • 

A  chronology  of  important  discoveries,  developments,  etc.,  in  iron  and 
steel  industry  dating  from  prehistoric  times  to  1919.  294  pages. 

Pcnton's  Foundry  List;  published  by  The  Penton  Publishing  Go.,  Cleve- 
land. (1922.) 

A  list  of  all  of  the  foundries  in  the  United  States  and  Canada, 
arranged  by  class  of  products.  A  separate  list  of  malleable  iron 
foundries  is  included.  896  pages. 

The  Romance  of  Modern  Manufacture,  by  Charles  R.  Gibson;  published 
by  Seeley  &  Co.,  Ltd. 

A  popular  account  of  the  marvels  oir  manufacturing.  Malleable  iron 
is  included.  320  pages,  illustrated. 

Index   of    the    Transactions   of    the   American    Foundrymen's    Association; 
American    Foundrymen's    Association,    Chicago.     (1921.) 
An  index  of  all  volumes  of  Transactions  from  IX  to  XXIX  inclusive, 
containing  hundreds   of   references   to   articles   on  malleable  iron.     An 
author's .  index  also  is  given.     192  pages. 

Foundrymen's  Handbook;  published  by  the  Penton  Publishing  Co.  (1922.) 
Contains  data  on  malleable  iron,  as  well  as  on  all  other  branches  of 
the  foundry  industry.  309  pages. 

Iron  and  Steel,  by  J.  H.  Stansbie ;  published  by  ^Constable  &  Co.,  Ltd. 

This  book  is  a  comprehensive  treatise  on  the  modern  aspects  of  iron 
and  steel  manufacture  together  with  an  account  of  its  history.  Mal- 
leable castings  are  included  in  the  text.  375  pages,  illustrated. 

The  Founder's  Manual,  by  David  W.  Payne;  published  by  D.  Van  Nos- 
trand  Co.,  New  York.  (1920.) 

A  handbook  for  foundrymen,  with  tables  on  mathematics,  weights  and 
measures,  materials,  alloys,  foundry  fuels,  cupola  practice,  sand, 
molding  practice,  etc.  One  brief  chapter  is  devoted  exclusively  to  mal- 
leable cast  iron.  676  pages,  245  illustrations,  and  list  of  coke  and 
anthracite  pig  irons  by  trade  names. 

Foundry  Cost  Accounting,  by  Robert  E.  Belt;  published  by  the  Penton 
Publishing  Co.  (1919.) 

The  twelve  chapters  cover  every  phase  of  accurate  cost  methods 
and  their  various  application  to  different  branches  of  the  foundry 
industry.  The  principles  and  forms  used,  the  classification  of  accounts, 

386  Selected  Bibliography 

the  methods  of  distributing  overhead  expenses,  the  procedures  used  to 
determine  the  cost  of  individual  jobs  or  classes  of  work,  are  such  that 
they  can  be  easily  adopted  to  fit  the  requirements  of  any  foundry — 
gray  iron,  malleable,  steel  or  nonferrous.  262  pages,  75  forms  and 

Co-operation  Between  the  Engineer  and  the  Malleable  Iron  Foundry,  by 
G.  F.  Meehan. 

A  discussion  of  the  need  of  teamwork  between  engineers  and  mal- 
leable foundrymen  to  insure  better  design  of  castings.  1000  words. 
Transactions,  A.  F.  A.,  Vol.  XXV,  p.  221. 

The  Commercial  Side  of  the  Malleable  Iron  Industry,  by  W.  G.  Kranz. 
A  brief  historical  sketch  of  the  industry,  followed  by  an  account  of 
recent  developments  (1916)  and  a  statement  covering  erroneous  con- 
ceptions of  the  properties  of  malleable  that  are  being  corrected. 
1000  words.  Transactions,  A.  F.  A.,  Vol.  XXV,  p.  501. 

British  and  American  Malleable  Cast  Iron,  by  T.  Turner. 

Theory  and  practice  are  discussed  and  futures  of  industries  in  Eng- 
land and  the  United  States  are  predicted.  Iron  Age,  Vol.  102,  p.  970. 

Improvements   in  Making   Malleable   Iron. 

A  review  of  recent  progress  (1919)  based  on  research  and  develop- 
ment work  of  American  Malleable  Castings  association.  Raw  Mate- 
rials, Vol.  1  (1919),  p.  443-8. 


The  A  B  C  of  Iron  and  Steel,  edited  by  A.  O.  Backert;  published  by  the 
Penton  Publishing  Co.,  Cleveland.  (1921.) 

Twenty-six  chapters  by  eminent  authorities  covering  manufacture  of 
iron  and  steel  from  mine  to  finished  product.  Contains  chapters  on 
making  gray  iron,  steel  and  malleable  castings,  the  latter  product  being 
covered  by  H.  A.  Schwartz.  408  pages,  269  illustrations,  numerous 
statistical  tables  and  index. 

The  Production  of  Malleable  Castings,  by  Richard  Moldenke.  (1910.) 
(Out  -of  print.) 

The  first  book  published  covering  the  production  of  malleable,  includ- 
ing history,  characteristics  of  malleable,  testing,  patternmaking,  mold- 
ing, melting,  equipment,  casting,  annealing  and  cost  of  malleable. 
125  pages,  35  illustrations. 

International  Library  of  Technology;  published  by  International  Text- 
book Co. 

Volume  on  "the  manufacture  of  gas,  iron,  steel  and  cement."  Con- 
tains information  on  malleable  iron. 

Non-Technical  Chats  on  Iron  and  Steel,  by  L.  W.  Spring;   F.   Stokes   Co. 
A    review,    in    popular    manner,    of    methods    of    producing    iron    and 

Selected  Bibliography  387 

steel  products,  with  a  reference  to  the  making  of  malleable  cast  iron. 

Malleable    Cast  Iron,  by    S.    J.    Parsons;    Constable   &   Co.,    Ltd.     (Tem- 
porarily out  of  print.)     Reprinting. 

Melting,  molding,  annealing  and  cleaning  operations  are  explained ; 
equipment  is  described,  and  principles  of  design  and  method  of  making 
patterns  discussed.  182  pages,  86  illustrations. 

Iron  and  Steel,  Vol.  I,  by  William  Henry  Greenwood;  Henry  Carey  Baird 

&  Co.  I  -jifi 

Refractory  materials,  iron  ores,  metallurgical  chemistry  of  iron,  pig 
iron,  blast  furnace  operation,  malleable  cast  iron,  production  of  mal- 
leable in  open  hearth.  255  pages,  illustrated. 

Notes  on  Foundry  Practice,  by  J.  J.  Morgan;  published  by  Charles  Grif- 
fin &  Co.,  Ltd.     (1912.) 

This  work  gives  a  general  description  of  the  methods  of  founding 
and  provides  condensed  and  reliable  information  as  to  the  material 
used  and  its  methods  followed  in  more  particularly  iron  founding. 
The  subject  of  malleable  castings  is  included.  104  pages,  24  illus- 

International   Library    of    Technology;    published    by    International    Text- 
book  Co. 

Volume  on  "machine  molding,  foundry  appliances,  malleable  castings, 
etc."  Contains  a  complete  chapter  of  36  pages  on  the  properties  and 
composition  of  malleable  cast  iron. 

General  Foundry  Practice,  by  William  Roxburgh;   Constable  &  Co.,  Ltd. 

A  treatise  on  general  iron  founding  with  notes  on  metallurgy,  melt- 
ing, molding,  heat  treatment,  cleaning,  etc.  Malleable  castings  are 
mentioned.  308  pages,  161  illustrations. 

General  Foundry  Practice,  by  A.  McWilliam  and  Percy  Longmuir ;   Chas. 
Griffin  &  Co.,  Ltd.     (1920.) 

Molding  sands,  foundry  equipment,  refractories,  mixing,  pouring,  heat 
treatment,  testing,  etc.,  as  applied  to  general  foundry  work.  Reference 
is  made  to  malleable  cast  iron.  384  pages  illustrated. 

Malleable  Cast  Iron,  by  Bradley   Stoiighton. 

A  brief  outline  of  the  methods  of  manufacture  and  properties  of  mal- 
leable cast  iron,  as  known  in  1908.  School  of  Mines  Quarterly 
(Columbia  Univ.),  Vol.  29,  p.  54. 

The  Production  of  Malleable  Castings,   by  Richard  Moldenke. 

A  brief  treatise  including  history  of  the  industry,  properties  of  mal- 
leable, metallurigcal  principles,  and  methods  of  production.  4500 
words.  An  address  before  Connecticut  Valley  Section  of  the  Amer- 
ican Chemical  Society,  Jan.  4,  1913.  Transactions,  A.  F.  A.,  Vol.  21, 
p.  815. 

388  Selected  Bibliography 

Some  of  the  Factors  in  the  Manufacture  of  High  Grade  Malleable  Cast- 
ings, by  J.  G.  Garrard. 

A  brief  discussion  of  the  difficulties  in  making  malleable  castings  of 
heavy  section.  Results  of  iron  produced  by  practically  eliminating  top 
blast  are  given.  800  words.  Transactions,  A.  F.  A.,  Vol.  XXVII, 
p.  370. 

Malleable  Iron — Its  Manufacture,  Characteristics  and  Uses,  by  J.  P.  Pero. 
Development  of  the  industry,  method  of  melting,  distinction  between 
shrinkage  and  contraction,  annealing  practice  and  specifications  are 
the  principal  topics  covered  in  this  paper.  3600  words.  Transactions, 
A.  F.  A,  Vol.  XXIII,  p.  451. 

An  Outline  to  Illustrate  the  Inter-dependent  Relationship  of  the  Variable 
Factors  in  Malleable  Iron  Production,  by  L.  E.  Gilmore. 
A  discussion  of  the  chemical  analysis  and  miscrostructure  of  white 
iron,  types  of  furnaces  employed,  quality  of  fuel,  control  of  combus- 
tion, ideal  mixtures,  heat-treating  and  annealing,  etc.  2800  words 
and  one  control  chart  of  operations.  Transactions,  A.  F.  A.,  Vol. 
XXIVi  p.  233. 

Progress  in  Manufacture  of  Malleable  Iron,  by  Enrique  Touceda. 

A  progress  report  of  recent  advances  in  the  technical  development  of 
the  malleable  industry  as  of  1920,  with  a  discussion  of  future  possi- 
bilities. Furnace  design  and  melting  practice,  and  improved  prop- 
erties of  product  are  discussed.  4500  words.  Transactions,  A.  F.  A., 
Vol.  XXIX,  p.  354. 

Fuel  and  Materials 

Burning  Liquid  Fuel,  by  W.  N.  Best ;  published  by  U.  P.  C.  Book  Co., 
Inc.  (1922.) 

History,  theory  and  applications  of  oil  fuel  in  28  chapters,  one  of 
which  (3500  words,  17  illustrations)  is  devoted  to  malleable  iron, 
gray  iron  and  brass  foundry  practice.  341  pages,  316  illustrations. 

Foundry  Irons,  by  Edward  Kirk;  Henry  Carey  Baird  &  Co.  (Out 
of  print.) 

History  of  ironmaking,  pig  iron  production,  mixing  irons,  casting  by 
direct  process,  foundry  chemistry,  analysis,  etc.,  as  applied  to  cast  iron 
and  malleable  cast  iron.  Three  chapters  are  devoted  to  malleable.  276 
pages ;  illustrated. 

Blast  Furnace  and  the  Manufacture  of  Pig  Iron,  by  Robert  Forsythe ; 
published  by  the  U.  U.  C.  Book  Co.  (1922.) 

An  elementary  treatise  for  the  use  of  the  metallurgical  students  and 
the  furnaceman.  Several  pages  are  devoted  to  malleable  pig  iron, 
castings  and  specifications.  368  pages. 

Fuel    and    Combustion,    by    Max    Sklovsky. 

A    general .  article    on    economy    of    combustion    which    in    conclusion 

Selected  Bibliography  389 

touches   on   tunnel   kilns    for  annealing   malleable   iron   castings.     2500 
words,  9  illustrations.     Transactions,  A.  F.  A.,  Vol.  XXIX,  p.  367. 
Coal — Its  Origin  and  Use  in  the  Air  Furnace,  by  F.  Van  O'Linda. 

The  properties  of  coal  for  air  furnace  melting  are  described  and 
suggestions  for  firing  given.  Cost  per  .B.t.u.  is  stated.  1600  words. 
Transactions,  A.  F.  A.,  Vol.  XXIV,  p.  251. 

Pulverized    Coal    for    Melting    Malleable    Iron,    by   W.    R.    Bean. 

An  explanation  of  the  factors  controlling  the  use  of  powdered  coal 
in  malleable  melting.  Foundry,  Vol.  45,  p.  487. 

Powdered  Coal  as  a  Fuel  in  the  Foundry,  by  A.  J.  Grindle. 

Uses  in  the  foundry,  problems  of  feeding  and  burning,  carburization, 
economy,  kind  of  coal  to  use,  preparing  fuel,  and  cost,  are  the 
principal  topics  discussed.  4000  words.  Transactions,  A.  F.  A.,  Vol. 
XXVIII,  p.  303. 

Efficient    Use    of    Pulverized    Coal    in    Malleable    Foundry    Practice,    by 
Milton  W.  Arrowood. 

The  author  discusses  methods  of  preparing  pulverized  fuel,  mixing 
it  with  the  air,  introducing  it  into  the  furnace,  and  controlling  furnace 
conditions.  The  theory  of  combustion  receives  considerable  attention. 
8400  words,  9  illustrations.  Transactions,  A.  F.  A.,  Vol.  XXVIII, 
p.  277. 

Plant  and  Equipment 

Foundry  Molding  Machines  and  Pattern  Equipment,  by  Edwin  S.  Carman; 
published  by  the  Penton  Publishing  Co.,  Cleveland.     (1920.) 
A    treatise    showing    the    use-  of    molding    machines    in    all    types    of 
foundries.     Parts  of  the  book  are  of   particular  interest  to  malleable 
foundrymen.     225    pages,    220    illustrations. 

Electric    Furnaces    in    the    Iron    and    Steel    Industry,    by    Rodenhauser- 
Schoenawa-Von  Baur;   published  by  John  Wiley  &  Sons.     (1920.) 
This  book  answers  clearly  and  untechnically  every  question  that  may 
arise   in  the  electric   steel   industry.     Malleable   iron   is    included.     460 
pages,   133  illustrations. 

A  Study  of  the  Malleable  Furnace,  by  Harbison-Walker  Refractories   Co. 
98  pages,  illustrated. 

A   Continuous   Malleable   Foundry. 

An  illustrated  description   of  the  new    (1911)    foundry  of  the   Crane 
Co.,   Chicago.     Foundry,  Vol.    38,   p.    1. 

Making  Large  Castings  from  Air  Furnace  Iron,  by  H.  E.  Diller. 

A   description   of   a    foundry   of   the   Westinghouse    company   equipped 
with  two  40  and  one   15-ton  air   furnaces.     Foundry    Vol    48    (1920) 
p.  973-77. 

A   New  Annealing  Furnace. 

Description   of    malleable   annealing    furnace   operated    by   the    Arcade 

390  Selected  Bibliography 

Malleable  Iron  Co.    Foundry,  Vol.  48    (1920),  p.  769-71. 

Foundry  Plant  and  Machinery,  by  J.  Horner. 

A  chapter  of  a  series.  This  chapter  is  devoted  to  the  equipment  and 
practice  in  malleable  foundries.  Engineering,  Vol.  90,  pp.  787-91. 

Annealing    Furnaces,    by    George    Rietkolter. 

A  description,  with  drawings,  of  malleable  annealing  furnaces.  Stahl 
und  Risen,  Vol.  27  (1908),  p.  1652. 

Malleable  Cast  Iron  and  the  Open-Hearth  Furnace,  by  G.  A.  Blume. 

A  description  of  two  open-hearths  built  in  a  malleable  plant  in  Fin- 
land in  1910-11.  The  operation  is  discussed  in  detail.  8000  words, 
3  illustrations.  Transactions,  A.  F.  A.,  Vol.  21,  p.  431. 

How  an  Oil  Fired  Malleable  Furnace  Operates. 

A  description  of  an  oil  fired  air  furnace  with  data  on  consumption, 
costs,  etc.  Foundry,  Vol.  45,  p.  503. 

The  25-Ton  Air  Furnace,  by  F.  C.  Rutz. 

A  brief  description  of  a  25-ton  furnace,  with  dimensions,  operating 
expense,  melting  ratio,  flexibility  of  operation,  etc.  800  words.  Trans- 
actions, A.  F.  A.,  Vol.  XXV,  p.  522. 

The  Waste   Heat   Boiler   for    Malleable   Furnaces. 

The  author  believes  waste  heat  installations  in  the  foundry  will  be 
justified  by  results.  Foundry,  Vol.  46,  p.  220. 

The  Theory  of  the  Modern  Waste-Heat  Boiler  and  the  Possible  Applica- 
tion of  Such  Boilers  to  Malleable  Melting  Furnaces,  by  Arthur  D. 

An  explanation  of  the  theory  of  the  waste  heat  boiler  and  a  descrip- 
tion of  the  installation  of  one  attached  to  an  air  furnace  at  the  Mc- 
Cormick  works  of  the  International  Harvester  Co.  The  performance 
of  this  boiler  is  given  and  results  tabulated.  600  words,  6  drawings 
and  charts.  Transactions,  A.  F.  A.,  Vol.  XXVI,  p.  349. 

Pointers  from  the -Practice  of  a  Malleable  Iron  Foundry. 

A  description  of  the  installation  of  waste  heat  boilers  on  air  furnaces 
at  the  plant  of  the  Buhl  Malleable  Co.,  Detroit  (1909),  1500  words, 
11  illustrations.  Castings,  Vol.  Ill,  p.  196. 

A  Modern  Coreroom,  by  Donald   S.   Barrows. 

A  description  of  the  coreroom  built  in  1918  at  the  malleable  plant 
of  the  T.  H.  Symington  Co.,  Rochester,  N.  Y.  2000  jyords,  10  illus- 
trations. Transactions,  A.  F.  A.,  Vol.  XXVII,  p. '429. 

A  New  Research  Department  for  a  Large  Malleable  Plant,  by  H.  A. 

A  description  of  the  laboratory  built  in  1919-20  by  the  National  Mal- 
leable Castings  Co.,  Cleveland.  The  laboratory  is  for  the  research 
requirements  of  a  group  of  scattered  foundries  and  the  article  lists 
and  describes  the  apparatus  and  outlines  the  arrangement  of  depart- 

Selected  Bibliography  391 

ments.  3700  words,  4  illustrations.  Transactions,  A.  F.  A.,  Vol. 
XXIX,  p.  380. 

Early   Laboratories    in   Malleable   Industry. 

Discussion  by  Richard  Moldenke  and  H.  A.  Schwartz  of  the  pioneer 
laboratories  of  1891  to  1903,  with  reference  to  the  work  of  Dr. 
Moldenke,  H.  E.  Diller,  A.  A.  Pope  and  others.  1200  words. 
Transactions,  A.  F.  A.,  Vol.  XXVII,  p.  400. 

Melting  Practice 

Calculating  Mixtures  for  Malleable  Cast  Iron,  by  Harrold  Hemenway. 
A  system  of  calculating  mixtures  is  fully  explained  and  the  impor- 
tance of  the  various  constituents  emphasized.  8000  words,  27  tables. 
Transactions,  A.  F.  A.,  Vol.  XXIII,  p.  413. 

Influence  of  Changing  the  Composition  of  Malleable  Castings,  by  P. 

Results  of  tests  showing  effects  of  additions  of  manganese,  silicon, 
aluminum,  titanium,  antimony  and  tin,  copper,  bismuth  and  lead, 
sulphur  and  phosphorus  to  malleable.  1000  words.  Transactions,  A. 
F.  A,  Vol.  XXII,  p.  201. 

Malleable  Troubles,  by  Richard  Moldenke. 

A  discussion  of  melting  problems,  particularly  those  related  to  the 
selection  of  iron,  use  of  scrap,  etc.  Annealing  also  is  discussed. 
3500  words.  Transactions,  A.  F.  A.,  Vol.  XXII,  p.  251. 

Effect  of  Varying  Silicon  and  Carbon  in  Malleable  Iron  Mixtures,  by 
A.  L.  Pollard. 

A  discussion  based  on  records  of  analyses  and  tests  covering  a  period 
of  8  months,  during  which  time  the  silicon  and  carbon  contents  were 
varied.  1200  words.  Transactions,  A.  F.  A.,  Vol.  XXIII,  p.  437. 

Titanium  for  Malleable  Iron,  by  C.  H.  Gale. 

Ferro-titanium  was  added  to  malleable-  in  the  ladle  and  tests  of  the 
resulting  product  made.  The  paper  is  a  discussion  of  the  results. 
2400  words,  5  tables.  Transactions,  A.  F.  A.,  Vol.  20,  p.  271. 

Malleable  Castings  by  a  New  Process   (1908),  by  E.  C.  Origley. 

Wrought  iron  and  soft  steel  are  melted  in  a  crucible,  the  metal  is 
quieted  by  additions,  and  poured.  Iron  Age,  Vol.  81,  p.  1312-13. 

Standardization   of    Air    Furnace    Practice,    by    A.    L.    Pollard. 

A  discussion  of  design,  touching  on  length  of  hearth,  depth  of  bath, 
length  of  firebox,  height  of  roof,  opening  at  neck  and  wall  thick- 
nesses. Advantages  and  disadvantages  are  compared  and  notes  on 
operation  presented.  1800  words.  Transactions,  A.  F.  A.,  Vol. 
XXIV,  p.  245. 

Melting  in  an  Air  Furnace  with  Fuel  Oil,  by  J.  P.  Pero. 

Disadvantages  are  compared  with  advantages,  and  data  on  oil-operated 

392  Selected,  Bibliography 

air  furnaces  in  three  plants  are  given  in  parallel.  2000  words,  1  table. 
Transactions,  A.  F.  A.,  Vol.  XXVIII,  p.  316. 

The  Equipment  of  Air  Furnaces  Using  Oil  as  Fuel,  by  W.  N.  Best. 

Method  of  changing  air  furnace  from  coal  firing  to  oil  firing,  with 
suggestions  regarding  design  of  burners  and  method  of  operation. 
1500  words.  Transactions,  A.  F.  A.,  Vol.  XX,  p.  421. 

The  Application  of   Pulverized   Coal   to   Malleable   Melting   Furnaces,   by 
Joseph  Harrington. 

The  author  discusses  factors  affecting  successful  use  of  pulverized 
coal  in  air  furnaces,  covering  rapidity  of  heating,  temperature,  effect 
on  furnace  lining,  amount  of  carbon  burned  out,  etc.  2600  words. 
Transactions,  A.  F.  A,  Vol.  XXVI,  p.  394. 

Application  of  Pulverized  Coal  to  the  Air  Furnace,  by  W.  R.  Bean. 

A  discussion  of  the  disadvantages  of  hand  firing  and  of  the  possi- 
bilities of  overcoming  some  of  them  by  using  pulverized  coal.  Meth- 
ods of  altering  air  furnaces  for  this  fuel  and  results  of  tests  are 
given.  2800  words.  Transactions,  A.  F.  A.,  Vol.  XXVI,  p.  337. 

The  Triplex    Process   of    Making    Electric   Furnace    Malleable,    by    H.    A. 

A  complete  description  of  the  triplex  process  invented  by  W.  G. 
Kranz  and  employed  by -the  National  Malleable  Castings  Co.  This 
process  involves  the  use  of  the  cupola,  converter  and  electric  furnace. 
3200  words,  5  illustrations.  Transactions,  A.  F.  A.,  Vol.  XXIX, 
p.  342. 

The  Refining  of  Cupola  Malleable  Iron  in  the  Electric  Furnace,  by  A.  W. 

The  advantages  of  cupola  melting  of  malleable  are  recounted,  and  the 
results  of  experiments  in  refining  the  cupola  metal  electrically  are 
presented  and  discussed.  2400  words,  3  illustrations.  Transactions, 
A.  F.  A,  Vol.  XXVIII,.  p.  322. 


Foundry  Work,  by  Burton  L.  Gray ;  published  by  the  American  Technical 
Society.     (1920.) 

A  practical  handbook  on  standard  foundry  practice,  including  hand 
and  machine  molding,  cast  iron,  malleable  iron,  steel  and  brass  cast- 
ing, foundry  managements,  etc.  224  pages,  191  illustrations. 

The  Control  of  Chill  in  Cast  Iron,  by  G.  M.  Thrasher. 

Bulletin,  A.   I.  M.   E.    (1915),  p.  2129. 
Malleable  Cast  Iron,  by  F.  Erbreich. 

Methods    of    molding    and    annealing    are    described    and    illustrated. 

Stahl  und  Eisen,  Vol.  35,  pp.  549-53,  652-58,  773-81. 
Producing  Machinable  Malleable  Iron  Castings,  by  A.   T.  Jeflfery. 

The  author  explains  how  to  avoid  common   machining  difficulties  by 

Selected  Bibliography  393 

adopting  good  foundry  practice.     Foundry,  Vol.  45,  p.  449. 

Gating   Malleable   Iron   Castings,   by  A.   M.   Fulton. 

Methods  of  properly  gating  malleable  castings  with  various  typical  sec- 
tions, avoiding  chills  wherever  possible.  Shrinkage  defects  are  dis- 
cussed. 2100  words,  9  illustrations.  Transactions,  A.  F.  A.,  Vol. 
XXV,  p.  239. 


A    Study   of    the    Annealing    Process    for    Malleable    Castings,    by    E.    L. 

A  review  of  the  metallography  of  white  cast  iron  is  followed  by  a 
description  of  tests  to  study  the  effects  of  different  packing  materials, 
of  different  annealing  temperatures,  of  different  times  of  annealing 
and  different  rates  of  cooling.  3200  words,  data  on  23  experiments, 
15  micrographs.  Transactions,  A.  F.  A.,  Vol.  XXII,  p.  169. 

Experiments   in  Annealing   Malleable  Iron,  by  H.   E.  Diller. 

The  author  discusses  the  two  actions  occurring  in  the  anneal,  and 
describes  tests  made  to  ascertain  proper  temperatures,  time,  rate  of 
cooling,  etc.  3000  words,  4  illustrations.  Transactions,  A.  F.  A., 
Vol.  XXVII,  p.  404. 

Continuous    Tunnel    Annealing,    by    Philip    d'H.    Dressier. 

A  description  of  the  Dressier  type  tunnel  annealing  furnace  for 
malleable  castings,  on  the  basis  of  its  development  in  1918.  2400 
words,  5  illustrations.  Transactions,  A.  F.  A.,  Vol.  XXVII,  p.  414. 

The  Application  of  Powdered  Coal  to  Malleable  Annealing  Furnaces,  by 
Charles    Longnecker. 

Following  a  brief  historical  sketch  of  the  subject,  the  author  describes 
the  installation  at  the  plant  of  the  Pressed  Steel  Car  Co.,  comparing 
results  with  those  obtained  by  the  use  of  natural  gas  and  fuel  oil. 
2100  words,  3  illustrations.  Transactions,  A.  F.  A.,  Vol.  XXVIII, 
p.  270. 

Effects    of    Annealing    Gray    and    Malleable    Iron    Bars    in    Copper    Oxide 
Packing,  by  H.   E.  Diller. 

Malleable  iron  bars  were  packed  in  black  oxide  of  copper  and  annealed 
in  an  experimental  furnace.  In  one  case  the  copper  soaked  through, 
the  bar  analyzing  21.4  per  cent  copper.  Similar  tests  at  various 
annealing  temperatures  are  described.  1600  words,  8  illustrations. 
Transactions,  A.  F.  A.,  Vol.  XXVIII,  p.  261. 

Malleable  Annealing  Experiments,  by  S.   B.  Chadsey. 

Results  of  tests  of  malleable  subjected  to  repeated  annealing.  Foundry, 
Vol.  37,  p.  215. 

Reducing  the  Malleable  Iron  Annealing  Period,  by  A.  E.  White  and  R.  S. 
Time  can  be  saved  by  raising  the  annealing  temperature  slightly  above 

394 Selected  Bibliography 

the  critical  point  and  maintaining  it  at  700  degrees  long  enough  to 
change  0.70  per  cent  combined  carbon  to  graphitic  carbon.  Foundry, 
Vol.  47,  p.  61. 

Graphitization  of  White  Cast  Iron  upon  Annealing,  by  Paul  D.  Merica  and 
Louis  J.  Gurevich. 

A  description  and  discussion  of  experiments  in  which  the  graphitiza- 
tion  ranges  of  temperatures  for  three  compositions  for  car  wheels 
were  determined.  Light  is  thrown  on  certain  moot  questions  of  the 
metallurgy  of  annealing.  2400  words,  7  illustrations.  Transactions, 
A.  I.  M.  M.  E.,  Vol.  LXII,  p.  509. 

The  Annealing  of  Malleable  Castings,  by  A.  E.  White  and  R.  S.  Archer. 
Following  a  discussion  of  the  constituents  of  malleable  castings,  the 
authors  describe  experiments  with  white  iron,  covering  the  time  of 
annealing,  the  temperature  and  method  of  treatment.  In  conclusion, 
the  authors  state  an  ideal  heating  cycle  is  impossible,  each  case  depend- 
ing on  local  requirements.  Transactions,  A.  F.  A.,  Vol.  27,  p.  351. 

Researches  in  the  Annealing  Process  for  Malleable  Castings,  by  Oliver 
W.  Storey. 

A  discussion  of  research  work  on  packing  materials,  temperature  of 
annealing,  time  of  annealing,  and  rate  of  cooling,  with  important  con- 
clusions. 4400  words,  10  micrographs.  Transactions,  A.  F.  A.,  Vol. 
XXIII,  p.  460. 

Copper  Diffuses   Through   Cast  Iron,  by  H.   E.  Diller. 

An  investigating  effect  of  oxidizing  packings  in  annealing  malleable,  it 
was  found  that  copper  penetrated  bar  packed  in  copper  oxide.  Foundry, 
Vol.  47  (1919),  p.  779-80. 

Production    of    Malleable    Castings,   by    Richard    Moldenke. 

An  extensive  discussion  of  the  principles  of  annealing,  with  data 
on  operation  and  description  of  apparatus.  The  Iron  Trade  Review, 
Vol.  44  (1910),  pp.  540,  776. 

Notes  on   Malleable  Cast  Iron,  by  R.  Namias. 

A  discussion  of  composition  of  metal,  rate  of  cooling  during  anneal, 
etc.  Engineering,  Vol.  88,  p.  669. 


Oxy-Acetylene  Welding  Manual,  by  Lorn  Campbell,  Jr.,  John  Wiley  & 
Sons,  Inc. 

Apparatus  and  methods  of  oxy-acetylene  welding  of  various  materials, 
including  malleable.  Glossary  of  welding  terms. 

Oxy-Acetylene  Welding  Practice,  by  Robert  J.  Kehl,  published  by  Amer- 
ican Technical  Society. 

A  practical  presentation  of  the  modern  processes  of  welding,  cutting 
and  lead  burning  with  special  attention  to  welding  technique  of 
different  metals.  Simple  and  complex  cases  of  expansion  and  con- 

Selected  Bibliography 395 

struction — preheating  steel,  cast  iron,  malleable  iron,  aluminum,  cop- 
per, brass  and  bronze  welding.  110  pages,  117  illustrations,  diagrams 
and  tables. 

Oxy- Acetylene  Welding,  by  S.  W.  Miller ;  Industrial  Press. 

Twelve  chapters  on  oxy -acetylene  welding  of  various  materials,  in- 
cluding malleable  cast  iron.  287  pages,  192  illustrations. 

Troubles   Encountered  in   Machining  Malleable   Iron:     Causes   and  Reme- 
dies, by  A.  T.  Jeffery. 

A  discussion  of  machining  difficulties  due  to  pure  hard  white  iron, 
under-annealed  iron,  iron  cooled  too  quickly,  burned  iron,  and  "tough 
and  stringy"  iron.  The  use  of  test  lugs,  effect  of  low  silicon,  etc., 
are  considered  and  in  summary,  the  author  urges  co-operation  between 
founder  and  user  of  castings.  2400  words,  7  illustrations.  Transac- 
tions, A.  F.  A,  Vol.  XXVI,  p.  383. 


The  Chemical  and  Metallographic  Examination  of  Iron,  Steel  and  Brass, 
by  Hall  and  Williams;  published  by  McGraw-Hill  Book  Co.  (1921.) 
Malleable  iron  is  included  in  the  volume.  500  pages,  illustrated. 

Cementation  of  Iron  and  Steel,  by  Frederico  Giolitti ;  published  by  Mc- 
Graw-Hill Book  Co.  (1915.) 

Information  on  the  theory  of  malleablized  castings.  407  pages,  illus- 

Cast  Iron  in  the  Light  of  Recent  Research,  by  William  H.  Hatfield; 
Charles  Griffin  &  Co.,  Ltd. 

The  iron-carbon  alloys  and  cast  iron  from  the  standpoint  of  the 
equilibrium  diagram,  with  chapters  on  the  influences  of  silicon,  phos- 
phorus, sulphur,  manganese,  etc.  Malleable  iron  is  given  considerable 
attention,  the  heat  treatment  of  white  iron,  influence  of  sulphur  on 
the  stability  of  iron  carbide  in  the  presence  of  silicon,  and  the  phos- 
phorus content  permissible  in  malleable  being  discussed.  Mechanical 
properties  of  malleable  are  outlined.  292  pages,  199  illustrations. 

An  Outline  of  the  Metallurgy  of  Iron  and  Steel,  by  A.  H.  Sexton  and 
J.  S.  G.  Primrose;  Scientific  Publishing  Co. 

An  outline  of  processes  of  iron  and  steelmaking,  with  a  discussion  of 
•    metallurgy  involved.     Malleable  iron  is  included.     587  pages,  271  illus- 

An  Elementary  Textbook  of  Metallurgy,  by  A.  Humbolt  Sexton;  pub- 
lished by  Charles  Griffin  &  Co.,  Ltd. 

This  work  is  intended  for  the  use  of  students,  both  for  those  com- 
mencing the  study  of  metallurgy  and  those  who  are  already  engaged 
in  metallurgical  industries  and  who  desire  some  knowledge  of  the 
principles  on  which  the  processes  they  are  using  are  based.  Mai- 

396  Selected  Bibliography 

leable  iron  is  taken  up  in  Part  I  under  metallurgical  processes.  263 
pages,  71  illustrations. 

Principles   of  Metallography,  by   Robert    S.   Williams;    published   by    Mc- 
Graw-Hill  Book   Co.     (1920.) 
Malleablizing   is   included  in  this  text.     158   pages. 

Practical   Metallography    of    Iron    and    Steel,    by    John    S.    G,    Primrose; 
published  by  Scientific  Publishing  Co. 
Contains    information   on   malleable   cast   iron.     129    pages,    illustrated. 

Methods    of    Chemical    Analysis    and    Foundry    Chemistry,   by    Frank    L. 
Crobaugh;    Penton    Publishing    Co.     (1910.) 

Sampling  and  preparation  of  samples;  determination  of  iron,  phos- 
phorus, sulphur,  etc.;  analysis,  etc.,  as  applied  to  white  and  chilled 
castings,  malleable  castings,  gray  iron  castings,  etc.  110  pages. 

The  Metallurgy  of  Iron  and  Steel,  by  Bradley   Stoughton ;   McGraw-Hill 
Book  Co.  "(1913.) 

Iron  and  carbon,  manufacture  of  pig  iron,  bessemer  process,  open- 
hearth  process,  defects  in  ingots  and  castings,  treatment  of  steel,  iron 
and  steel  founding,  constitution  of  cast  iron,  malleable  cast  iron,  intro- 
duction to  metallurgy,  etc.  539  pages,  illustrated. 

Metallurgy  of  Iron  and  Steel,  by  A.  Humbold  Sexton ;  published  by  Scien- 
tific  Publishing   Co. 

This  book  covers  in  one  volume  the  whole  field  of  metallurgy  of  iron 
and  steel.  Method  of  making  malleable  iron  is  described.  600  pages, 
270  illustrations. 

Metallurgy  of  Iron,  by  Thomas   Turner ;   published  by   Charles   Griffin   & 
Co,    Ltd.     (1920.) 

Contains  information  on  the  production  of  malleable  cast  iron.  486 
pages,  illustrated. 

The   Metallography    of   Steel   and    Cast   Iron,   by    Henry    Marion    Howe; 
McGraw-Hill    Book    Co.,    New    York.     (1916.) 

A  finished  treatise  on  general  metallography,  with  numerous  references 
to  malleable  iron.  641  pages,  hundreds  of  illustrations,  numerous 
tables  and  diagrams,  and  complete  indices. 

The  Metallography  and  Heat  Treatment  of  Iron  and  Steel,  by  Albert 
Sauveur;  Sauveur  and  Boylston,  Cambridge,  Mass.  (1916.) 
A  thorough  study  of  metallography  covering  all  types  of  iron  and 
steel.  One  chapter  is  devoted  exclusively  to  malleable  cast  iron,  and 
several  others  are  pertinent  to  malleable  producers  and  users.  486 
pages,  437  illustrations. 

Metallography  Applied  to  Siderurgic  Products,  by  Humbert  Savoia;   pub- 
lished by  E.  &  F.  N;  Spon,  Ltd. 

A  complete  chapter  of  23  pages  is  devoted  to  malleable  cast  iron.  180 
pages,  illustrated. 

Selected  Bibliography  397 

Metallography,    by    Arthur    H.    Hiorus ;    published    by    Macmillan    &    Co. 

An  introduction  to  the  study  of  the  structure  of  metals  chiefly  by  the 
aid  of  the  microscope.  Several  pages  are  given  over  to  malleable  cast 
iron.  158  pages,  illustrated. 

Iron  and  Steel,  by  O.  F.  Hudson;    Constable  &   Co.,   Ltd. 

An  introductory  textbook  for  engineers  and  metallurgists.  Methods  of 
production  are  not  covered  in  this  book.  Metallurgy  of  malleable  cast 
iron  is  discussed  briefly.  184  pages,  47  illustrations. 

Fractures  and  Microstructures  of  American  Malleable  Cast  Iron,  by  W.  R. 
Bean,  H.  W.  Highriter  and  E.   S.  Davenport. 

A  discussion  of  typical  specimens  of  malleable  cast  iron  based  on 
chemical,  miscroscopic  and  mechanical  examination.  6500  words,  40 
illustrations.  Transactions,  A.  F.  A.,  Vol.  XXIX,  p.  306. 

Some  Remarks  Regarding  the  Permissible   Phosphorus  Limit  in  Malleable 
Iron  Castings,  by  Enrique  Touceda. 

Dynamic  tests  of  malleable  containing  .181,  .252,  .325  and  .388  per 
cent  phosphorus  were  made,  and  the  author  interprets  the  results  for 
the  guidance  of  malleable  foundrymen.  3500  words,  5  illustrations,  2 
tables.  Transactions,  A.  F.  A.,  Vol.  XXIV,  p.  209. 

Report  on  Methods  of  Etching  Malleable  Iron  for  Visual  Investigation  of 
Structure,  by  E.  Heyn. 

The  author  recommends  a  solution  of  1  gram  of  copper-ammonium 
chloride  in  12  grams  of  water.  Etching  requires  a  minute.  1500 
words,  8  illustrations.  International  Association  of  Testing  Materials, 
Brussels,  1906. 

Change  of  Structure  in  Iron  and  Steel,  by  William  Campbell. 

Review  of  iron-carbon  equilibrium  diagram,  illustrated  by  photomi- 
crographs of  irons  and  steels.  Journal,  Franklin  institute,  Vol.  163, 
pp.  407-34. 

Constitution  of  the  Iron-Carbon  Alloys. 

A  discussion  of  Sauveur's  article  in  Journal  of  Iron  and  Steel  insti- 
tute by  Benedicts,  who  upholds  Roozeboom's  application  of  phase  rule. 
Also  discussed  by  Howe,  Stansfeld,  Stead  and  others.  Mctallurgie, 
Vol.  4,  pp.  216-41. 

Influence  of   Silicon  upon  the  Iron-Carbon  System. 

Author  determines  amount  of  carbon  remaining  in  solution  after 
adding  definite  amounts  of  silicon  to  molten  pig  iron.  Influence  of 
silicon  upon  solidification  point  also  determined.  Stahl  und  Eiscn, 
Vol.  27,  482-87. 

Note  on  the  Liquids  in  the  Iron-Carbon  Diagram,  by   G.   Cesaro. 

Discussion  of  an  attempt  to  determine  the  course  of  the  curve  joining 
the  points  at  which  molten  iron-carbon  alloys  begin  to  solidify.  Jour- 
nal, Iron  and  Steel  Institute.  (1919.) 

398  Selected  Bibliography 

The  Alloys  of  Iron  and  of  Carbon,  by  Georges  Charpy. 

A  lecture  on  the  iron-carbon  system,  in  which  the  author  reviews  the 
knowledge  of  the  subject  as  of  1909.  Bulletin  de  la  Socicte  Chimique 
de  France,  Vol.  3,  p.  i-xlvi. 

Some  Iron-Silicon-Carbon  Alloys,  by  W.  Gontermann. 

A  review  of  binary  systems  contributing  to  the  above  equilibrium, 
with  the  author's  theory  on  the  Fe-C  system.  Zeitschrift  fur  anor- 
gische  Chemie.  Vol.  59  (1909),  p.  373-414. 

Development  of  the  Fusion  Diagram  of  Iron-Carbon  Alloys,  by  F.  Wust 
An  explanation  of  the  theory  underlying  the  construction  of  the  fusion 
diagram.  The  author  proposes  the  term  "Ledeburite."  Zeitschrift 
fur  Elektrochimie,  Vol.  15  (1910),  p.  565-584. 

Chemical  Equilibrium  in  the  Reduction  and  Cementation  of  Iron,  by  Ru- 
dolph Schenck. 

Zeitschrift  fur  Elektrochimie,  Vol.  21  (1915),  p.  37;  Vol.  22  (1916), 
p.  121;  Vol.  24  (1918),  p.  248. 

Separation  of  Graphite  in  White  Cast  Iron  Heated  under  Pressure,  by 
Georges  Charpy. 

Change  of  carbide  to  graphite  when  the  metal  is  subjected  to  high 
pressure  and  a  temperature  of  from  700  to  1000  degrees.  Cotnptes 
Rendus,  Vol.  148  (1909),  p.  1767. 

The  Stable  System:  Iron-Carbon,  by  Rudolf  Ruer  and  Nikolaus  Iljin. 
A  thorough  discussion  covering  the  solubility  of   carbon  in  solid  iron 
and  the  separation  of  temper  carbon.    Metallurgie,  Vol.  8,  p.  97. 

The   System   Iron-Carbon,  by   A.    Baikov. 

A  study  of  the  solidification  of  iron  showing  that  separation  of 
graphite  and  cementite  follows  the  same  line  on  the  diagram.  Revue 
de  Metallurgie,  Vol.  8,  p.  315. 

The  Solubility  of  Carbon  in  Iron,  by  O.  Ruff  and  O.  Goecke. 

A  discussion  attending  the  determination  of  the  solubility  of  carbon 
in  iron  at  temperatures  between  1200  and  2600  degrees  Cent.  Metal- 
lurgie, Vol.  8,  p.  417. 

The    Equilibrium    Diagram    of    Iron-Carbon    Alloys,    by    Otto    Ruff. 
Metallurgie,  Vol.  8,  pp.  456-64,  497-508. 

A  Study  of  the  Annealing  Process  for  Malleable  Castings,  by  Oliver  W. 

The  effects  of  packing  material,  temperature  of  annealing,  time  of 
annealing  and  rate  of  cooling  are  studied.  A  thorough  and  original 
discussion  on  annealing.  Metallurgical  and  Chemical  Engineering, 
Vol.  12,  p.  383. 

The  Nature  of  the  A2  Transformation  in  Iron,  by  K.  Honda. 

A  study  of  recent  investigations.  Scientific  Reports,  Tohoku  Imperial 
University,  Vol.  4  (1915),  p.  169. 

Selected  Bibliography  399 

Phosphorus    Limit   in    Malleable    Castings,   by    Enrique    Touceda. 

The  author  describes  tests  which  showed  that  when  combined  carbon 
was  low,  evil  effects  of  phosphorus  were  slow  to  make  themselves 
felt.  Iron  Age,  Vol.  96,  p.  92. 

Sulphur  in  Malleable  Cast  Iron,  by  R.  H.  Smith. 

The  author  concludes  that  sulphur  is  not  removed  in  the  annealing, 
process  and  does  not  appear  to  have  evil  effects  below  0.15  per  cent. 
Journal,  Iron  and  Steel  Institute.  Vol.  92,  p.  141. 

Recrystallization  after  Plastic  Deformation,  by  H.  M.  Howe. 
Bulletin,  A.  I.  M.  E.   (1916),  p.  1851-60. 

Decarburization  of  Iron-Carbon  Alloys,  by  W.  H.  Hatfield. 

The  author  opposes  theory  that  carbon  must  be  in  the  form  of  temper 
carbon  before  it  can  be  removed  by  oxidation.  Engineering.,  Vol.  87 
(1910),  p.  801. 

Graphitization   of    Iron-Carbon   Alloys,    by    Kotaro    Honda    and   Takejiro 

In  pure  iron  carbon  alloys,  graphitization  is  caused  by  the  decom- 
position of  the  cementite  solidified  during  cooling  from  the  melt. 
Journal,  Iron  and  Steel  Institute  (Sept.).  (1920.) 

Graphitizing  of  White  Cast  Iron,  by  R.   S.  Archer. 

The  author  draws  conclusions  regarding  the  initiation  of  graphitiza- 
tion below  the  A  point  and  completion  near  or  at  that  point.  Foundry, 
Vol.  48  (1920),  p.  192-4. 

Concerning  the  Solubility  of  Graphite  in  Iron,  by  Carl  Benedicts. 

Tests  show  that  graphite  is  appreciably  soluble  in  ferrite  at  940 
degrees  Cent.,  therefore,  iron-carbon  diagram  should  be  drawn  as  pro- 
posed by  LeChatelier,  Stansfield  and  Charpy.  Metallurgie,  Vol.  5 
(1908),  p.  41-45. 

Influence  of  Phosphorus  on  the  Iron-Carbon  System,  by  F.  Wust. 

The  subject  is  brought  up  to  date  (1908)  and  results  of  tests  and 
experiments  are  given.  Metallurgie,  Vol.  5,  p.  73-87. 

The  Nature  of  the  Cast  Irons,  by  G.  B.  Upton. 

Discussion  of  Fe-C  diagram,  relating  particularly  to  liquidus  and 
solidus  lines.  Journal  of  Physical  Chemistry,  Vol.  13  (1909),  p. 

The  Effect  of   Foreign   Substances   Upon  the   Fusion   Diagram  of    Iron- 
Carbon  Alloys,  by  P.  Goerens. 

An  investigation  of  the  iron-manganese-carbon  and  iron-phosphorus- 
carbon  systems.  Metallurgie,  Vol.  6  (1910),  p.  537-50. 

Theory  of   Malleablizing,   by  W.   H.   Hatfield. 

The  European  and  American  methods  of  making  malleable  castings 
are  described.  From  a  lecture  before  Institution  of  Engineers  and 
Shipbuilders  of  Scotland.  Foundry,  Vol.  36,  p.  30. 

400  Selected  Bibliography 

Graphitization  in  Iron-Carbon  Alloys,  by  Kunlichi  Tawara  and  G.  Ashara. 
Twenty-seven  iron-carbon  alloys  were  melted  and  after  slight  cooling 
cast  into  molds  and  cooled  at  varying  rates.  Deductions  from  these 
tests  are  discussed.  Journal,  Iron  and  Steel  Institute  (1919). 

The   Theory   of    Annealing,   by    F.    Wust. 

A  discussion  of  the  metallurgy  of  annealing  with  special  reference  to 
the  migration  of  carbon.  Metallurgie,  Vol.  5  (1908),  p.  7-12. 

The  Evolution  of  the  Malleable  Iron  Process,  by  J.  P.  Pero  and  J.  C. 

An  account  of  the  advance  in  metallurgy  of  malleable  practice,  touch- 
ing upon  the  importance  of  sulphur  and  phosphorus,  "steely"  iron, 
uses  of  the  microscope,  value  of  strength  tests,  fatigue  failure,  and 
properties  of  malleable.  4000  words.  Transactions,  A.  F.  A.,  Vol. 
XXV,  p.  222. 

What  Is  the  Normal  Fracture  of  Good  Malleable  Iron?  by  Enrique 

The  author  explains  how  the  test  lug  should  be  secured  and  describes 
the  appearance  of  various  fractures,  interpreting  the  significance  of 
each.  2000  words,  6  illustrations.  Transactions,  A.  F.  A.,  Vol.  XXV, 
p.  506. 

Judging   Malleable  by  Fracture,  by  Richard   Moldenke. 

Photographs  of  typical  fractures,  with  suitable  explanation  of  each. 
Foundry,  Vol.  37,  p.  237. 


Materials  of  Construction,  by  Adelbert  P.  Mills ;  published  by  John  Wiley 
&  Sons,  Inc.,  New  York.  (1922.) 

Manufacture  and  uses  of  cements,  clay  products,  ferrous  and  non- 
ferrous  metals,  timber,  rope  and  mechanical  fabrics.  One  chapter 
(2500  words),  devoted  to  malleable  cast  iron,  describes  methods  of 
production  and  lists  properties  and  uses. 

Materials  of  Construction,  by  M.  O.  Withey  and  James  Aston ;  John  Wiley 
&  Sons,  Inc.  (1918.) 

Principles  of  mechanics  of  materials  including  timber,  stone,  cement, 
metals,  etc.  Constitution  of  iron  and  steel  and  the  properties  of  metal 
products,  including  malleable  cast  iron.  840  pages,  illustrated. 

Machinability  of  Malleable  Cast  Iron. 

A  discussion  of  the  paper  by  Messrs.  Smith  and  Barr  (A.  F.  A.  Vol. 
XXVIII,  p.  330),  covering  threading  tests  and  data  on  cutting 
speeds.  1700  words.  Transactions,  A.  F.  A.,  Vol.  XXVIII,  p.  338. 

Relation  Between  Machining  Qualities  of  Malleable  Castings  and  Physical 
Tests,  by  Edwin   K.    Smith  and  William   Barr. 

A  discussion  of  the  effect  of  higher  physical  properties  of  malleable 
upon  its  machinability,  based  on  the  results  of  tests  and  replies  to  a 

Selected  Bibliography  401 

questionnaire.  2100  words,  2  drawings  and  5  tables.  Transactions, 
A.  F.  A.,  Vol.  XXVIII,  p.  330. 

Some  Physical  Constants  of  American  Malleable  Cast  Iron,  by  H.  A. 

A  review  of  the  properties  of  malleable  with  detailed  data  and 
charts  showing  the  behavior  of  the  metal  under  various  stresses  and 
physical  conditions.  5000  words,  12  diagrams.  Proceedings,  A,  S.  T. 
M.,  Vol.  XIX,  Part  II,  p.  248. 

Physical  Properties  of  American  Malleable  Cast  Iron,  by  W.  R.  Bean. 
A  discussion  of  the  strength,  elongation,  resistance  to  bending,  hard- 
ness, machinability,  density,  etc.,  of  malleable.  2400  words,  3  illus- 
trations, 3  tables.  Proceedings,  A.  S.  T.  M.,  Vol.  XIX  Part  II,  p. 

Testing   Hardness   of    Malleable,   by   Enrique   Touceda. 

The  author  explains  why  hardness  tests  are  inadequate  as  a  measure 
of  machinability.  1000  words,  2  illustrations.  Proceedings,  A.  S.  T. 
M.,  Vol.  XIX;  Part  II,  p.  273. 

Effect  of  Machining  and  of  Cross  Section  on  the  Tensile  Properties  of 
Malleable  Cast  Iron,  by  H.  A.  Schwartz. 

A  description  of  tests  made  to  determine  the  effect  of  decarbonization, 
grain  structure,  area  of  cross  section,  rate  of  cooling,  shrinkage,  etc., 
on  the  relative  strength  of  a  specimen.  The  results  are  discussed  and 
conclusions  drawn.  2400  words,  6  diagrams.  Proceedings,  A.  S.  T. 
M.,  Vol.  XX ;  Part  II,  p.  70. 

Standard    Specifications    for    Malleable    Castings    (A   47-19). 

The  standard  specifications  adopted  in  1919  by  the  American  Society 
for  Testing  Materials.  800  words,  1  illustration.  A.  S.  T.  M. 
Standards,  1921,  p.  354. 

Some  Needs  of  the  Malleable  Iron  Industry,  by  W.   P.   Putnam. 

The  author  explains  that  research  must  be  extended  and  equipment 
improved  before  malleable  practice  attains  a  high  standard  of  'excel- 
lence. 1500  words.  Transactions,  A.  F.  A.,  Vol.  XXVIII,  p.  257. 

Malleable  Iron  as  a  Material  for  Engineering  Construction,  by  H.  A. 

A  review  of  certain  objections  to  malleable  held  by  engineers  in  1918, 
followed  by  a  brief  outline  of  the  malleable  process,  a  detailed  account 
of  metallurgical  principles  involved,  and  a  description  of  the  actual 
properties  of  malleable  as  an  engineering  material.  7500  words,  15 
illustrations.  Transactions,  A.  F.  A.,  Vol.  XXVII,  p.  373. 

Malleable   Iron  and   Its   Uses,  by  Henry  F.   Pope. 

A  brief  outline  of  the  characteristics  of  malleable  and  its  principal 
applications  as  an  engineering  material.  1500  words.  Year  Book, 
A.  I.  and  S.  I.,  1917,  p.  353. 

Remarks  on  the  Strength  and  Ductility  of  Malleable  Cast  Iron  After  the 

402  Selected  Bibliography 

Skin  Has   Been  Removed,  by  Enrique   Touceda. 

An  expose  of  the  fallacy  that  after  the  skin  of  a  malleable  casting 
has  been  removed,  the  remaining  metal  is  of  inferior  quality.  4000 
words,  3  illustrations.  Transactions,  A.  F.  A.,  Vol.  XXIII,  p.  440. 

Chemical  and  Physical  Properties  of  Malleable  Iron,  by  W.  P.  Putnam. 
The  annealing  process  is  discussed  and  charts  are  shown  to  empha- 
.size  the  importance  of  closely  controlling  annealing  temperatures.  500 
words,  5  charts,  2  tables,  4  micrographs.  Transactions,  A.  F.  A.,  Vol. 
20,  p.  363. 

The  Physical  Properties  of  Malleable  Castings  as  Influenced  by  the 
Process  of  Manufacture,  by  Richard  Moldenke. 

An  argument  for  the  adoption  of  standard  specifications  for  malleable, 
particularly  to  control  time  of  annealing,  1100  words,  Proceedings, 
A.  S.  T.  M.,  Vol.  3,  p.  204. 

Physical  Constants  for  Malleable  Cast  Iron  by  H.  A.  Schwartz. 

Results  of  tests  on  the  physical  properties  of  malleable.  Foundry, 
Vol.  47,  p.  462. 

Properties  of  Malleable  Cast  Iron,  by  H.  A.   Schwartz. 

An  outline  of  the  mechanical,  thermal  and  electrical  properties  of 
American  malleable.  Engineering  Nezvs-Record,  Vol.  83,  p.  132. 

The  Use  to  Which  Malleable  Iron  Castings  Can  Be  Applied  in  Car 
Construction,  by  Frank  J.  Lanahan. 

A  historical  sketch  covering  the  types  of  castings  used  in  construc- 
tion of  American  railroad  cars,  followed  by  a  discussion  of  the 
merits  of  malleable  castings  for  this  work.  3200  words.  Transac- 
tions, A.  F.  A.,  Vol.  XXV,  p.  489. 

Advantages  of  Malleable  Iron  Versus  Steel  for  Agricultural  Castings, 
by  P.  A.  Paulson. 

An  explanation  of  the  increased  use  (in  1918)  of  malleable  castings 
in  agricultural  machinery,  with  reference  to  the  tensile  strength  of 
malleable,  uniformity  of  metal,  and  ratio  of  elastic  limit  to  the 
tensile  strength.  1200  words.  Transactions,  A.  F.  A.,  Vol.  XXVII, 
p.  425. 

The  Integrity  of  the   Casting,  by   Enrique   Touceda. 

A  discussion  of  the  value  of  tests  to  determine  the  properties  of 
malleable,  with  comments  on  the  production  of  sound  castings.  2400 
words.  Transactions,  A.  F.  A.,  Vol.  XXVII,  p.  438. 

Effect  of  Machining  and  of  Cross-Section  on  the  Tensile  Properties  of 
Malleable  Cast  Iron,  by  H.  A.  Schwartz. 

A  study  of  tensile  properties  of  malleable.  Proceedings,  American 
Society  for  Testing  Materials,  Vol.  20  (1921),  p.  70-79. 

Tests  for  Hardness,  by  T.  Turner. 

An  investigation  to  compare  results  obtained  by  Turner,  Shore,  Brinell 
and  Keep  methods.  Engineering,  Vol.  87  (1909),  p.  835. 


Agricultural    implements,    applications    of    malleable    for     37 

Air   Furnace: 

Action  of  flame  in 141 

Amount  of  air  required  for  combustion 145 

Analysis  of  slag  in    147 

Chemical    changes    in    melting   in    146 

Chemistry  of  combustion   in    146 

Coal  consumption  of 144 

Consumption  of  refractories    147 

Depth  of  metal   in 143 

Design  of   125,  136 

Dimensions  of    143 

Heat  balance  of    153 

Historical    notes    on    early 135 

Method   of  firing  and  melting   in *. 138 

Rate  of  melting  in 157 

Roof  construction  of   141 

Use  of  forced  draft 154 

Use    of   pulverized    coal    in - 154 

Temperature    of   metal    in 152 

Variation  in  composition  at  different  periods  of  heat  in 150 

Alexander    46 

American    Malleable    Castings    Association: 

Research    work    of 31,  35 

Tensile  properties  of  specimens  submitted  by  members  of 291 

American   Malleable   Castings   Co 19 

American    Radiator    Co 21 

American    Society    for    Testing    Materials: 

Adoption  of  specifications  for  malleable 36 

Specifications    for    malleable    castings 274,  276 


Changes  of  metallographic  composition  of  white  iron  during....  69 

Cycle,    length    of    218 

Effect  of  type  of  packing  for 228 

Factors  affecting  the  rate  of  cooling  during 220 

Factors  affecting  height  of,  stacks  of  pots 192 

Function    of   packing    in 190 

404  Index , 

Annealing : 

Furnace,    consumption    of    coal    in 203 

Furnace,  description  and  use  of  pit  type  of 199 

Furnace,   design   of 194 

Furnace,  disposition  of  heat  in 205 

Furnace,    economy    of    large 195 

Furnace,    electric    heating    arrangement    suggested    by    Touceda 

for  use  in    208 

Furnace,    heat    requirements    of    204 

Furnace,    pyrometer    equipment    for 209,  210 

Furnace,    thermal    efficiency    of 206 

Furnace,  use  of  powdered  coal  for 196 

Limitations    on   minimum   time   of 221 

Metallurgy    of    61,  230 

Method  of  packing  castings   for 190 

Objections  to  high  temperature  at  beginning  of 214 

Operations,   outline  of    81 

Pots,   construction   of 193 

Pots,    life    of 192 

Pots,  separator  plate  for 193 

Practice,   early   conception   of 189 

Principles    of 213 

Range  of  temperatures  in 189 

Safe   maximum   temperature    for 215 

Temperature,   controlling    209 

Archer,    R.    S 33,  46,  63,  65,  349 

Ash,  analysis  of,  of  suitable  coal  for  melting 115 

Austenite,    definition    of 41 

Austin     51 

Automotive  industry,  use  of  malleable  in 38 

Barlow,  J.  H.,   successor  of  Boyden 16 

Barr,   William    - 330,  331,  334 

Bauer,     0 231 

Bean,  W.  R ' 30,  32,  263,  273,  295 

Beams,   strength   of  malleable   castings    when   used   as 307 

Beckett,   James    29 

Beilby     349 

Belgium,  production  of  malleable  in     40 

Benedick's    diagram    47,  51 

Index  405 

Bessemer  process,    effect   of   discovery   of 6 

Bibliography      385 

Black  heart   malleable,   discovery  of,   by   Boyden 11 

Blast    furnace: 

Pig  iron  first  made  in,  in  Germany 4 

Probable   facts    surrounding   introduction    of   first,    in   prehistoric 

period    3 

Blast  furnaces,   location  of,  making  malleable   pig  iron 96 


As    a    metallurgist 26 

Extracts  from  diary  kept  by 11 

Foundry    career    of    15 

Statue  of,   erected  by  citizens  of  Newark,    N.  J. . 12 

Successors  of   16 

Boyden,  Seth  95,  197 

Bourcoud,  A.   E 231 


Analysis  of  burnt   131 

Manufacture  of  fire 131 

Bridgeport  Malleable   Iron    Co. 18 

Brinell    method    of    measuring    hardness     '. .  324 

Brittleness,  tests  by  Humphrey  on 322 

Building  requirements,  comparison  of,  for  gray  iron  and  malleable 

plants    .- 83 

Campbell,    H.    H 182 

Canada,   production    of    malleable    in 39 

Capacity  of  malleable   plants   in  United    States 84 


Conversion    of    combined,    into    temper 66,67 

Definition  of  temper r 41 

Effect   of,   on    tensile    properties    of   malleable 292 

Graphite   and   temper,   in   graphitization 52 

Methods  of  determining,   content 270 

Migration   of,   during   annealing   process 222,  224 

Recombination  of,  in  pig  iron,  under  melting  conditions 137,  139 

Relation    between    silicon    and,    in    malleable 55,  68 

Solubility    of    65 

Study  of  quantitative  effect  of,  by  author  in   1904 30 

Cast  iron,  first  production  of,  in  early  stack  or  blast  furnace 4 

406  Index 

Cementite,   definition   of 41 

Cesaro    46,  235 

Charpy    33 

Chicago  Malleable   Iron    Co 19,  94 

Chrome    269 


Analysis    of    raw    refractory. 131 

Location    of    deposits    of    refractory     126,  127,  129 

Use  of  refractory,  in  malleable  industry    127,  129 

Cleaning  castings,  methods  of 249 

Cleveland  Malleable  Iron  Co 19 


Analysis    of    melting     113 

Consumption    of,    in    annealing    203 

Consumption    of,   in   air   furnace   melting 144 

Distribution    of    sources    of 109,  1 10 

Factors  to  be   considered  in   selecting,   for  melting 113 

Grades  of,  used  in  malleable  foundries Ill 

Method    of    preparing    pulverized 117 

Precautions  to  be  taken  in  transporting  pulverized 117 

Requirements   in,    for    pulverizing 115 

Size  of,  for  air  furnace  fuel 115 

Use  of  pulverized,  in  air  furnace  melting 154 

Coke,  use  of,  in  making  malleable  in   cupola 121 

Color  method,  unreliability  of,  for  determining  carbon  and  silicon  267 

Columns,   strength   of  malleable    cast 305 

Combustion,  discussion  of,  in  air  furnace 145 

Compression,  behavior  of  malleable  under 303,  304 

Contraction : 

Effect  of  size  and  shape  of  casting  on,  of  metal 242 

Use  of  terms   "fluid,"  and   "solid" 237 

Converter,  type  of,  used  in  triplex  process 167 

Coonley,  John  C 19 

Corrosion    of    malleable - 376 

Cort,  invention  of  puddling,  furnace  by 6 

Cross   bending: 

Behavior   of  malleable   under   cyclic 357,  358 

Results  of  tests  on,  of  malleable 309 

Stresses  in,  of  malleable 307 

Index  407 

Crum-Grzimailo 141 


Control    of    metal    in,    melting 175 

Metallurgy  of  melting  in 163,  177 

Ratio  of  metal  to  fuel  in 177 

Cutting   hardness,   method   of   measuring 327 

Dalby    : .355 

Davenport,   E.   S 273 

Dayton    Malleable    Iron    Co .' 19 


Control  of,  in  annealing 226 

Extent    of,    during   annealing    process 224 

Definitions  of  entities   in   alloys   of  iron  and  steel 41 

Density  of  malleable 384 

Design,   factors  to  be  considered  in,   of  malleable  castings    243 

Devlin,  Thomas 17,  28 

Diller,   H.    E 29 

Dolomite,   use   of,    in   malleable    industry 133 

Dressier-type  tunnel  kiln  for  annealing 202,  206 

Drill  tests,  conclusions  drawn  from,  of  malleable 331,  332 

Dyer,    C.    D 138 

Eastern    Malleable    Iron    Co 18 

Eberhard    Mfg.    Co 21 

Elastic   Limit: 

Definition  of 287 

Increase  in,  of  malleable  by  plastic  deformation 356 

Electric   Furnace: 

Chemical     advantages     of 160 

Chemical  reactions   in    164 

Description   of,   used   in   triplex   furnace 163 

Distribution  of  metalloids  in 171 

Use  of,  in  malleable  industry 160 

Electrical  properties  of  malleable 371 

Electrical  resistance  of  malleable,  effect  of  temperature  on 376,  377 

Elongation,   effect  of,   on   resistance   of  malleable   to   dynamic  ten- 
sile loads 319 

England,  production  of  malleable  in 39 

Equilibrium  diagram   for  iron   carbon   system 47,  48,  49,  63 

408 Index 

Equipment,   principal,    used    in    malleable    foundries 73 

Expansion   of   malleable    378,  379 

Fairchild 209 

Fatigue,   resistance   of  malleable    to 323 

Feeders,   use   of,   in   molding  malleable    castings 245 

Ferrite,     definition     of     41 

Ferromanganese,  use  of,  in  making  malleable 105 

Ferrosilicon,  use  of,  in  making  malleable 107 

Fire    brick,    manufacture    of 131 

Foote      209 

Forbes,    Alexander    Duncan 18 

Forbes,  Duncan    18,  28 

Forquignon 33 

Fort  Pitt  Malleable  Iron  Co 183 

Foundries : 

Distribution    of   malleable,    in    United    States ....20,23 

Number  of  malleable,  in  the  United   States 24 

Range   in  size  and  capacity  of  malleable 71 

Fracture : 

Interpreting  appearance   of 148,  149,  150 

Normal,    of    malleable    iron 279 

France,   production  of  malleable   in 40 

Freezing,    changes    of   metallographic    composition    of    white    iron 

during , 69 

Friction,  resistance  of  malleable  to 336 

Fryer,  J.  H 193 

Fuel,  classification   of,  used  in  making  malleable 109 

Fulton,    A.    M 182 

Furnace,  primitive  iron,  used  by  early  Egyptians 2,  3 

Furnace,  shoveling,  built  by  Seth  Boyden 197 

Galvanizing,  method  of  hot,  of  malleable 263 


Analysis  and  properties  of,  for  melting  purposes 119 

Composition  of  producer 119 

Location   of  producing   fields    of   natural 110 

Gailly,    Raymond    40 

Gates,  proper  use  of,   in  molding  malleable 245 

General  Electric   Co.    ,  21 

Index 409 

Goecke    •** 

Gontermann . . ; 52,  234 

Goodlet,   James    95 

Gordon     • 51 

Graphite,    definition    of 41 


Effect   of   chemical   composition    on 52 

Relation  of  time  and  temperature  in 68 

Research    on,    by    Storey 33 

Theory  advanced  by  Honda  and  Murakami 35 

Theory  of 61 

Grenet    33 

Grinding,  precautions  to  be  taken  in  disk,  of  malleable  castings..  254 

Grinding  as  a  method  of  removing  gates,   fins,  etc 253 

Hammer,  Alfred  E 27,  29,  30,  34,  97 

Harding,     Warren     G 19 


Method  of  measuring   cutting 328 

Methods   of  measuring 324 

Relation  of  Brinell  and  Shore,  numbers 326 

Relation    of,   to    completeness    of   anneal 326 

Relation  of,  to  wear  of  malleable 324 

Significance    of    cutting,    of    malleable     327 

Harness,  early  application  of  malleable  for,  parts 36 

Harrison     209 

Haswell,  John    18 

Hatfield,     W.     H 10,  33 

Heat    balance    of    triplex    process 171,  172,   173 

Heat,   disposition   of,   in   annealing  furnace 205 

Heat  treatment  of  malleable  at  temperatures  below  critical  point..   264 

Herbert   328,  329 

Heyn,   E 33 

Highriter,   H.   W 137,  273 

Hird 52 

Honda,    Kotaro     35 

Hoosick  Malleable  Iron  Works 17,   18 

Horsley,    Sidney    18 

Howe,   H.    M 33,  49,  63 

Iljin     33 

410 Index 


Effect  of,  on  malleable 315 

Machines  for  testing 322 

Testing  malleable  for,   by  series  of  equal  or   increasing  blows..  363 

Testing  malleable  for  resistance  to 316,  317 

Inspecting,   methods   of,   malleable 267 

Inspecting,   factors   to   be    considered   in,   malleable   for   acceptance 

by   consumer    283 

International    Harvester    Co 21 

Iron   and   steel   in   us'e   at   time   of   American    civil    war,    review   of 

types  of   6 

Iron-carbon    alloys,    theories    on 46 

Iron-carbon    diagram    47,  48,  49,  51,  63,  66 

Ironton   Malleable  Iron   Co % 19 

Japan,   production   of  malleable   in 40 

Jeffries,    Zay    46,  349 

Johnson,    Isaac    ; 17 

Johnson,  J.    B.,   Jr 101 

Kawahigashi,    Commander     40 

Kingsland,    G.    H ' , 197 

Kranz,  W.  G 160 

Labor,   division  of,   in  typical  malleable  plant 84 

Labor,  types  of,  available  in  various  foundry  centers  of  the  United 

States    87 

Laboratory,  A.  E.  Hammer  establishes  first  chemical,  in  American 

malleable    industry     27 

Laboratory,  McConway  &  Torley  establish 29 

LaMarche,  Charles  L 21 

Lanahan,    Frank   J 182 

Link-Belt    Co 21 

Load-deformation    curves    for    malleable    under    plastic    deforma- 
tion     364,  367,  368 

Loeb,    Peter    19 

Machineabilit}',  investigations  on,  of  malleable 328 


Factors   contributing  to,   difficulties 256 

Factors   governing,   of  malleable   castings 254 

Properties     of     malleable 330,  331 

Index 411 

Magnesia,  use  of,  as   refractory  in  malleable   industry 133 

Magnetic  properties  of  malleable 374,  375 

Magnetization    of  'malleable 373 


Contraction    from    pattern    size 240 

Discovery  of  black  heart,  by  Boyden  in  1826 11 

Early  uses  of   36 

Industry,  extent  of,  in   Europe 10 

Industry  in  Europe  resulting  from  Reaumur's  discovery 9 

Industry,  number  of  foundries  in  United 'States 24 

Industry,  present  extent  and  distribution  of  foundries  in 20,  23 

Iron,  first  described  by  Reaumur  in  1772 9 

Location    and    distribution    of    principal     sellers    of,    in    United 

States     22,  23 

Metallurgical   characteristics   of 46 

Misconceptions    regarding 31 

Pig   iron,    guarantees    of    analyses    of 103 

Production  of,  in  foreign  countries 39,  40 

Production    of,    in    United    States 23,  24 

Scrap,  description  of  grades  of 91 

Use  of,   for  electrical  apparatus 371 

Uses  of,  in  war   38 

Manganese,    method    of    determining,    consent 270 

Manganese  sulphide,  effect   of 57 

Martensite,  definition  of   41 

Material,  amount  handled  to  produce  one  ton  of  castings 85 

Material,  raw,  used  in  malleable  foundry 73 

Matsubara    230,  231 

McConway  &  Torley,  establish  laboratory 29 

Melting    operations,    outline    of . 77 

Melting    stock    used    in    making    malleable 91 

Merica,  P.  D 33,  63 

Metallography,  employment  of,  for  testing  malleable 273 

Metallography,  method  of  polishing  specimens   for 273 

Metallurgy,  brief  history  of  contributions  to,  of  malleable 33 

Metallurgy,  role  of,  in  development  of  American  malleable  industry     26 

Metals    used    by   prehistoric   metallurgists 1 

Meteoric  iron  discovered   by  Admiral   Peary 1 

Microstructure  of  malleable 59,  63 

Moldenke,   Dr.    Richard    .  .29,  30,  32,  97,  138 

412 Index 

Molding,   comparison   of  considerations  in,   of  gray  iron  and   mal- 
leable castings    233 

Molding  machines,  types  used  for  malleable  castings 247 

Molding  methods,  improvements  in 247 

Molding  sands,  location  of  beds  of,  in  United  States 124,  126 

Muffle  furnace,  description  of,  for  annealing 199,  200,  201 

Murakami,    T ' 35 

Mystery  in  malleable  industry 26 

National    Malleable     Castings     Co 19,  29,  95 

New  Jersey  Malleable  Works 17 

Newbold,   Charles    -....' 19 

Nichols,  W.  S 17 

Nicholson     328 

Northern  Malleable  Iron  Co 18 

Nutting    351,  353 


Location  of  supplies  in  the  United  States 110 

Use  of,  for  melting  and  annealing 123 

Use   of  fuel,    in   open-hearth    furnace 187 

Open-Hearth  Furnace: 

Advantages  and  disadvantages  of  melting  in ' 177 

Design     of 179,  180,  181 

Effect  of  invention  of,  by  Siemens 6 

Heat  balance  of  melting  in 185,  186 

Labor  required  to  operate 187 

Losses  in  melting  in 184 

Metallurgy     of      183 

Ordnance,  applications  of  malleable  for 38 

Ore,  analysis  of,   used  for   malleable 103 

Ore,  location  of  fields  supplying,  for  malleable  industry 96,   101 

Operations,   sequence   of,   in   malleable   foundries 77,  83 

Organization  of  malleable   foundry 72,  73 

Otis,    Frank  J 18 

Oxidation,   effect  of,   during  annealing    68 


Analyses  of  various  types  of,  for  annealing 229 

Composition    of,   used   for   annealing 228 

For  annealing,  metallurgical  effect  of  use  of 227 

Index 413 

Patterns  for  malleable,   factors   to   be   considered  in   making 241 

Payne    .. . . , 51 

Pearlite,     definition     of 41 

Permeability  of  malleable   372,  373 

Personnel   of   malleable   foundry    organization 73 

Peterson     235 

Phosphorus,    effect    of,    in   malleable    59 

Phosphorus,  method  of  determining,  content 270 

Pig  Iron: 

Discussion  of  merits  of  coke  and  charcoal 97 

First  made  in  blast  furnace  in  Germany  in  1311 :       4 

Grades  of,  used  in  making  malleable 95 

Guarantees  of  analyses  of  malleable 103 

Location  of  furnaces  making  malleable 96 

Tendency  toward  change  in  sulphur  and  phosphorus  content  of  105 

Pipe  fitting,  use  of  malleable  for 37 

Plastic    Deformation: 

Action  of  specimen  under  test  for 360 

Behavior  of  malleable  when  tested  for 340 

Change  of  structure  of  malleable  when  deformed  under 342 

Destroying   effect   of,    by    heat    treatment 345 

Effect  of,  on  elastic  limit ._ 356 

Effect  of,  on  grain  structure  of 343 

Mechanical    effects    of     349,351 

Theory  of   339 

Pope,   Alfred  A 19,  27,  29,  30,  34 

Press  fitting,  method  of,  malleable 257 

Production  of  malleable  in  foreign  countries. .  , 39 

Production  of  malleable  in  United  States  by  states 23,  24 

Production  of  steel  and  malleable  castings  compared 24 

Proportional    limit,    definition    of 287 

Protecting  coatings,  comparative  value  of  galvanizing,  sherardizing 

and    electrogalvanizing    262 

Protective  coatings,  methods  of  applying,  .to  malleable 262 

Puddling  furnace,  effect  of  invention  of,  by  Cort 6 

Pulverized  coal,  use  of,  in  annealing  ovens 196 

Pyrometers  for  annealing  furnaces 209,  210 

Railroad,  application   of  malleable   for,   rolling   stock    36 

Reaumur,   malleable   cast   iron  described  by    9 

414  Index 

Reduction  in  area,  relation  of,  to  diameter  of  tensile  test  specimen  298 

Refractories,    consumption   of,   in    air    furnace    melting 147 

Refractories,  use  of,  in  malleable  industry 127,  129 

Remy,     Marcel     40 

Roberts-Austin    diagram     46 

Rockford  Malleable  Iron  Works 19 

Ruff 33 

Ruer,    R 33 


Properties    of    molding 124 

Selection   of  core   and  molding,    for   malleable 245 

Tests    for   molding.  . 127 

Schenk 230,  231 

Scrap,   kinds   of,   used   in   making  malleable 91 

Shear,   behavior   of  malleable   when    subjected   to 310 

Shore  method  of  measuring  hardness 325 

Shrinkage,   allowance   for,    in    malleable 239 

Shrinkage,  use  of  term  in   molding  and  patternmaking 237 

Shrinks,   methods    of   avoiding 243 

Siemens,  effect  of  development  of  open-hearth  furnace  by 6 


Influence  of,  on  graphitization 53 

Method  of  determining,   content 270 

Range  of,  best  suited  to  foundry  requirements 54 

Relation    between    carbon    and,    in    malleable 55,  68 

Smith,    Edwin    K     330,  331,  334 

Sorbite,  definition  of   .  . , 41 

Specific  heat  of  malleable 381 

Sprue,  use  of,  as  melting  charge 94 

Steel  scrap,  selection  of,  for  charging  melting  furnace 94 

Steel,  use  of  "blister"  or  cementation,   in   early  centuries 5 

Steinmetz,    Charles    P 374 

Storey,   Oliver 33 

Straightening,  methods   of,  malleable   castings 261 

Sulphur,,  influence  of,   in  malleable 57 

Sulphur,    method    of    determining,    content    270 

Taylor,    F.   W 328,  329 


Effect  of,  on  dimensions  of  malleable 378 

Index 415 

Temperature : 

Influence  of,  on  graphitization 65 

Pouring,  for  malleable 235 

Use  of  malleable  under  high  378 

Tensile  properties  of  malleable,  effect  of  temperature   on 382 

Tensile   strength: 

Calculating   safe,   for   threaded    malleable 301 

Effect  of  carbon  on,  of  malleable 292 

Effect  of  cross  sectional  area  of  specimen  on 295,  297 

Relation  of,  of  cast  and  machined  specimens 295,  296 

Tension : 

Applying  alternate,    stress    to    malleable 356 

Behavior   of  malleable   iron    under 290 

Behavior    of    metals    under 288 

Stress-strain    diagram    of    malleable    under    successive    increas- 
ing     354,  355 

Test,  dynamic,  for  malleable  developed  by  B.  J.  Walker 321 

Test    lugs,    preparation    of 277 

Testing  machines,  types  of  impact 322 

Thermal   conductivity   of   malleable 379,  380,  383,384 

Thermo-couples,    use   of,    in    annealing   furnaces 210 

Thompson,    G.    H 18 

Thrasher    68 

Time    element    in    graphitization 68 

Timken   Roller   Bearing   Co.,   foundry  of 19 

Tool  failures,  causes  of,  in  machining  malleable 335 

Torsion  and  tension,  effect  on  malleable  of  combined 362 

Torsion,  behavior  of  malleable  when  subjected  to 311,  312,  313 

Touceda,    Enrique 29,  31,  32,  153,  208 

Triplex    Process: 

Description   of 161 

Developed   by  W.    G.   Kranz .' 160 

Heat  efficiency  of 174 

Metallurgy  of 162 

Metallurgy  of  slag  in 170 

Troosite,  definition  of 41 

Tunnel-kiln,    Dressier,    for    annealing. 202,  206 

Turner,  Thomas    40,  237,  327 

Tuttle,   B.   B.    .  18 

416 Index 

University  of    Illinois 328 

Walker,   B.    J 29,  34,  196,  321 

Wear,  relation  of  hardness  of  malleable  to 324 

Welding,    factors   to    be   considered   in,   malleable    castings 251 

Welding,  suggestions  to  user  of  malleable  castings  on 260 

White,  A.   E 33,  63 

White    cast    iron,    changes    of    metallographic    composition    during 

freezing  and  annealing   . .  .' 69 

White   cast   iron,    freezing   of . 49 

White  heart  malleable,  early  production  of,  in  United  States 10 

Whittemore,  J.   H ' ....17,  18,  19 

Wilmington   Malleable   Iron  Works 197 

Wood  Harvester  Co.,  Walter 18 

Wood   Mowing  &  Reaping  Machine   Co.,   Walter 18,  29 

Wood,  Walter ? 17,  28 

Woody,  W.   L 240 

Woodworking  tools,   impression  malleable  is  widely  used  for 38 

Wrought  iron,  early  use  of,  in  making  malleable 95 

Wust     235 

Yield  point,  definition  of 287 










Overdues  subject  to  replacement  charges 

FORM  NO.  DD1 1 ,  80m,  8/80  BERKELEY,  CA  94720